Learn Hardcore Chinese: lǎoshī zài kèshàng jiěshì le wèntí de yuányīn, yě shuō qīngchu le kěnéng de jiéguǒ. - In class the teacher explained the cause of the problem and also clearly stated the possible result.

在课上
- Common, natural in speech and writing.
- Emphasizes the activity while class is going on.
- 在课上解释了… = “explained (it) in class.”
课上 (without 在)
- Often used too, especially in more concise or written style.
- 老师课上解释了… is possible, but 在课上 sounds smoother in everyday speech.
课堂上 / 在课堂上
- Slightly more formal or written.
- 课堂 literally “classroom / class session.”
- 在课堂上解释了… feels a bit more like “in the classroom context” or “in the lesson.”
上课的时候
- Literally “when (we) were having class / during class time.”
- More explicitly temporal: 老师上课的时候解释了…
- Slightly longer; you feel the “when …” meaning more clearly.

In most everyday contexts, 在课上 and 上课的时候 can both translate as “during class,” but 在课上 is shorter and more compact.

What is 的 doing in 问题的原因 and 可能的结果? Is it like the English word “of”?

Yes, 的 here works very much like a linker, similar to English “of” or the ’s possessive.

问题的原因
- Literally: “the problem’s cause”
- Natural English: “the cause of the problem”
可能的结果
- Literally: “possible result(s)”
- 可能 = possible; 结果 = result
- 的 lets 可能 act as an adjective modifying 结果.

In grammar terms:

[Noun] + 的 + [Noun] → “the X of Y / Y’s X”
- 问题的原因 = 问题 (problem) + 的
  - 原因 (cause)
[Adjective or adjective‑like word] + 的 + [Noun] → “adjective + noun”
- 可能的结果 = “possible result(s)”

So yes, 的 here is basically “of” / possessive or “-’s,” and also a marker that allows 可能 to modify 结果.

Why is it 问题的原因 and not 原因的问题 if it means “the cause of the problem”?

Chinese and English organize these relationships differently.

English often says: cause of the problem → [CAUSE] of [PROBLEM]
Chinese usually says: 问题的原因 → [PROBLEM] 的 [CAUSE]

So the “owner” or the “base thing” usually comes before 的:

问题的原因 = “the problem’s cause”
书的作者 = “the book’s author”
公司的老板 = “the company’s boss”

原因的问题 would literally be “the problem of the cause,” which implies:

either “a problem with the cause,”
or “the issue concerning the cause,”

not simply “the cause of the problem.” So the normal and correct form for “the cause of the problem” is 问题的原因.

Why are there two 了 in the sentence (解释了…, 说清楚了…)? What does each 了 do?

Each 了 is an aspect particle attached to a verb phrase to show that the action is completed:

解释了问题的原因
- 解释了 = “(has) explained” / “explained” (completed action)
说清楚了可能的结果
- 说清楚了 = “(has) made clear / clearly stated” (also a completed action)

So we have two separate completed actions:

The teacher explained the cause.
The teacher clearly stated the possible results.

Each 了 marks completion of its own verb phrase. They are not one big sentence‑final 了; they are each bound to the verb.

Do these 了 mean past tense? Could this sentence ever describe the future?

了 marks aspect (completed action), not tense by itself.

In context, 解释了, 说清楚了 usually refer to completed actions, so they often get translated into past tense in English: “explained,” “made clear.”
But Chinese tense is mostly given by context (time words like 昨天, 刚才, 明天) or understood from the situation.

This sentence, as written, naturally describes a past or just‑completed situation (e.g., what happened in today’s class). To talk about the future, you would usually not use 了, and you would add a future context marker:

老师明天在课上解释问题的原因，也会说清楚可能的结果。
“The teacher will explain the cause of the problem in class tomorrow and will also clearly state the possible results.”

What exactly does 说清楚 mean? How is it different from just 说 or from 清楚地说?

说清楚 is a verb + result complement structure:

说 = say / speak
清楚 = clear(ly)
说清楚 = “to say (something) so that it becomes clear,” i.e. to make it clear through saying / to explain clearly.

Key differences:

说
- Basic “to say / to speak.”
- Doesn’t itself say whether the listener understands.
说清楚
- Implies the result: what was said is clear and understandable.
- Focus is on the outcome (clarity), not just the action of speaking.
清楚地说
- Grammatically: adverb + verb = “to speak clearly” (focus on manner).
- Describes how you spoke, but does not necessarily guarantee that the listener ended up understanding.
- In practice, it can overlap in meaning, but 说清楚 is more about “make it clear” as an accomplished result.

So 说清楚了可能的结果 = “(he) made the possible results clear.” It emphasizes that clarity was achieved.

Why does the sentence use both 解释 and 说清楚? Aren’t they both “explain”?

They are related but highlight slightly different things:

解释
- “to explain” in the sense of provide an explanation or interpretation, often about reasons, principles, meanings.
- 解释原因 = “explain the cause / reason.”
说清楚
- “to make clear by saying,” emphasize the clarity and completeness of what’s said.
- Often used for details, consequences, conditions, instructions, etc.
- 说清楚结果 = “clearly state the results / spell out the outcomes.”

So the teacher:

解释了问题的原因 – gave an explanation of why the problem happened.
说清楚了可能的结果 – clearly spelled out what might happen as a result.

Using two different verbs makes the sentence feel more precise and less repetitive.

What does 也 do here? Could we use 还 or 又 instead?

也 connects two actions by the same subject, adding the meaning “also / too / as well.”

老师在课上解释了问题的原因，也说清楚了可能的结果。
“The teacher explained the cause of the problem and also clearly stated the possible results.”

Compare:

也
- Neutral “also,” often used in writing and speech.
- Emphasizes that in addition to A, B also happened.
还
- Often suggests “in addition and on top of that”, sometimes with a sense of “even more / and what’s more”.
- 老师在课上解释了问题的原因，还说清楚了可能的结果。 is possible and natural, maybe sounding a bit more “and on top of that” / “furthermore.”
又
- Typically used for repeated actions (happening again), or for multiple negative/undesirable qualities (又贵又难吃).
- Here, 又 would sound odd, because we’re not talking about repetition or a list of properties.

So 也 is the most straightforward and neutral choice in this sentence.

After 说清楚了, there is no direct object pronoun like 它们. What is the object of 说清楚了 here?

The object is understood from context and therefore can be omitted, which is very common in Chinese.

The full, explicit form could be:

也说清楚了可能的结果（这些可能的结果）
- “also clearly explained these possible results.”

But since 可能的结果 is already mentioned right after, Chinese doesn’t need to repeat a pronoun:

说清楚了可能的结果 already expresses “made the possible results clear.”

More generally, Chinese often drops objects (and even subjects) when they are obvious from context:

吃了吗？ (Have you eaten?) – object 饭 is omitted.
看过了。 (I’ve seen [it].) – object is omitted.

Here, the understood object is the content being said: 可能的结果.

Does 结果 here mean one result or several? How do we know if it is singular or plural?

Chinese nouns usually don’t mark singular or plural unless you add specific words. So 结果 by itself can mean:

“result” (singular),
or “results” (plural).

In 可能的结果, it’s naturally interpreted as “possible result(s)”:

It can mean one possible outcome,
or a list of several possible outcomes.

If you really want to force a plural sense, you might add something like:

一些可能的结果 – some possible results
各种可能的结果 – various possible results

But in everyday language, 可能的结果 is usually understood as a set of possible outcomes, so English “possible results” is a good translation.

Why is the order 老师在课上解释了…，也说清楚了… and not something like 在课上老师解释了…?

Both orders are grammatically possible, but the most natural, common order is:

[Subject] + [time/place phrase] + [verb + object]

So:

老师在课上解释了问题的原因，也说清楚了可能的结果。
- 老师 = subject
- 在课上 = time/place
- 解释了…，也说清楚了… = predicates

You can say:

在课上，老师解释了问题的原因，也说清楚了可能的结果。

Here you put the time phrase 在课上 at the front for emphasis (like “During class, the teacher…”). This is also natural, especially in writing or when you want to highlight “during class” first.

But “在课上老师解释了…” without a comma or pause sounds a bit less standard; if you front 在课上, it’s more natural to mark a pause (written with a comma):

在课上，老师…

Could we omit 在课上? Would the sentence still be correct?

Yes, you can omit 在课上 and the sentence is still grammatically correct:

老师解释了问题的原因，也说清楚了可能的结果。
“The teacher explained the cause of the problem and also clearly stated the possible results.”

The difference is:

With 在课上: You specify when/where this happened – during class.
Without 在课上: You just state what the teacher did, with no explicit time/place.

So whether you include it depends on how important that context is to what you’re saying.