Learn Hardcore Chinese: tā zài zuò zhè gè ma?

Here, 在 before a verb marks an action in progress (the “-ing” aspect): 在 + 做 ≈ “be doing.” The same character 在 can also mean “at/in” as a preposition (“at a place”), but in this sentence it’s the progressive-aspect marker: 他在做… = “He is doing … (right now).”

Can I use 正在 instead of 在? What’s the difference between 在, 正, and 正在?

在 + V: the default progressive, neutral.
正在 + V: stronger emphasis on “right now, at this very moment.”
正 + V: also emphasizes “right in the middle of,” slightly more literary/emphatic. All are fine: 他在做这个吗？/ 他正在做这个吗？/ 他正做这个吗？ The meaning is similar; 正在 is the most explicit. You can also add 呢 at the end for extra “ongoing” feel: 他在做这个呢。

What changes if I drop 在 and say 他做这个吗？

Without 在, it’s no longer necessarily about “right now.” 他做这个吗？ can mean “Does he do this (in general)? / Will he do this?” It asks about habit, willingness, or future, not an action currently in progress.

How do I negate this naturally?

To negate the progressive, use 没(有):
- 他没在做这个。/ 他没有在做这个。 = “He isn’t doing this (now).”
不 is for habitual/refusal or scheduled facts, not a current ongoing action:
- 他不做这个。 = “He doesn’t do this / He won’t do this.” So: progressive → 没(有)在 + V; general/habitual → 不 + V.

What are natural short answers to this yes/no question?

Affirmative: 在。/ 他在（做）。/ 他在做（这个）。
Negative: 没在。/ 没有。/ 他没在做（这个）。
Avoid answering with 是/不是 unless the question used 是不是. Mandarin often repeats the verb or uses 在/没在 rather than a stand-alone “yes/no.”

Where does 吗 go? Can I ask the same question without 吗?

吗 is a sentence-final particle: it goes at the end, as in 他在做这个吗？
Without 吗, it’s a statement: 他在做这个。
You can ask without 吗 using:
- A-not-A: 他是不是在做这个？
- Intonation (often expressing surprise/confirmation): 他在做这个？

Why is 个 needed after 这? Could I just say 他在做这吗？

Chinese needs a classifier after demonstratives. 这 + (classifier) + [noun]. When the noun is omitted and you mean “this one/this thing,” the generic classifier 个 stands in: 这个.

他在做这个吗？ = “Is he doing this (one/thing)?”
他在做这吗？ is unnatural.
If you specify the noun, use the right classifier: 这件事 (this matter), 这道题 (this problem), etc.

Could I use a more specific classifier here?

Yes, if you name the noun:

他在做这件事吗？ (this matter; classifier 件)
他在做这道题吗？ (this question; classifier 道)
他在做这个项目吗？ (this project; generic 个 is fine with 项目) When the noun is omitted and you just mean “this (one),” use 这个.

How do you pronounce each word? Any tone or sandhi tips?

他 tā (1st tone)
在 zài (4th)
做 zuò (4th)
这 zhè (4th); before a classifier many say colloquial zhèi
个 gè (4th), often neutral tone here: ge
吗 ma (neutral tone)
Connected: “tā zài zuò zhè(ì) ge ma?”
Tip: With negation 不
- 4th-tone verb (e.g., 不做), 不 becomes rising: bú zuò. 没 has no such change.

Can I use 着 (zhe) for the progressive, like 他做着这个吗？

No. 着 marks a continuing state (e.g., 坐着, “be sitting”; 穿着, “be wearing”), not an activity-in-progress in general. Use 在/正在 + 做 for “be doing.” You can also add 呢 at the end: 他在做这个呢。

Is the word order fixed? Can I front 这个?

Default order is Subject + 在 + Verb + Object + 吗: 他在做这个吗？
Topicalization is common: 这个，他在做吗？ (“As for this, is he doing it?”)
You can omit the object if understood: 他在做吗？

Does 这个 mean a physical thing or can it mean a task/issue?

Both, depending on context:

Physical: 他在做这个模型吗？ (this model)
Task/matter: 他在做这件事吗？/ 他在处理这件事吗？
Project: 他在做这个项目吗？ Plain 这个 by itself can mean “this one/this thing/this matter.”

What’s the difference between 他在做这个吗？ and 他是不是在做这个？

他在做这个吗？ is a neutral yes–no question.
他是不是在做这个？ (A-not-A with 是不是) sounds more confirmatory or pressing: “Is he or isn’t he doing this?” Both are common.

If I want to emphasize “right now,” what should I add?

Use 现在 or 正在:

他现在在做这个吗？
他正在做这个吗？ Both make the “at this moment” meaning explicit; 正在 is the strongest built-in cue.

Can I use 干 instead of 做?

Often yes. 干 (gàn) is a colloquial substitute for “do/work on”:

他在干这个吗？ It’s more casual/blunt than 做. Prefer 做 in neutral/formal contexts.

Is using 有 for the progressive (他有在做这个吗) okay?

In Taiwan Mandarin, 有在 + V is a colloquial progressive: 他有在做这个吗？
In Mainland Mandarin it sounds dialectal; stick to 在/正在 + V as your default.

Does the final 吗 change the intonation?

Yes. With 吗, Mandarin typically ends with a slight fall; you don’t need a strong rising English-like pitch. Without 吗, a rising intonation can form a question, often conveying surprise/confirmation: 他在做这个？

Why are there spaces between characters here? I don’t see spaces in real Chinese.

The spaces are for teaching segmentation (words/morphemes). In normal writing you’d write it as 他在做这个吗？ without spaces.