kenkyuusitu de zikken wo sita ato, kyouzyu ni situmon wo simasita.

で marks the place where an action happens.

So in 研究室で, the meaning is in the laboratory / in the research lab, as the location where the experiment was done.

A useful comparison:

• で = where an action takes place
• に = destination, existence, or specific target in many cases

Here, since doing an experiment is an action, で is the natural particle.

• 研究室で実験をした = did an experiment in the lab

を marks the direct object of the verb.

In 実験をした, the thing being done is the experiment, so 実験 is marked by を.

This is very common with する:

• 勉強をする = to study
• 運動をする = to exercise
• 質問をする = to ask a question / ask questions
• 実験をする = to do an experiment

Even though English may sometimes phrase this differently, in Japanese noun + をする is a very common pattern.

Because あと in this sentence follows the plain past form of the verb.

The pattern is:

• Vた + あと(で) = after doing V

So:

• する → した
• したあと = after doing

That is why:

• 実験をしたあと = after doing the experiment

By contrast, て-form is used in other kinds of connections, but あと normally pairs with the past/plain form like this.

Here, あと means after.

More specifically, 実験をしたあと means after having done the experiment or simply after the experiment.

It shows the sequence:

1. did the experiment
2. asked the professor a question

A common grammar pattern is:

• Nのあとで = after N
• Vたあとで = after doing V

In this sentence, it is the verb version: したあと.

Yes, したあとで is also natural.

• 実験をしたあと、教授に質問をしました。
• 実験をしたあとで、教授に質問をしました。

Both mean basically the same thing: After doing the experiment, I asked the professor a question / questions.

The で in あとで often makes the expression sound slightly more complete or explicit, but in many sentences the difference is very small. In everyday Japanese, both are common.

Here, に marks the person the question was directed to.

So:

• 教授に質問をしました = asked the professor a question / asked the professor questions

In this kind of sentence, に often marks the target or recipient of the action.

Compare:

• 先生に聞きました = asked the teacher
• 友だちに話しました = spoke to a friend
• 教授に質問しました = asked the professor a question

So 教授に means to the professor or of the professor, depending on how natural English expresses it.

Both are possible.

• 質問をしました
• 質問しました

Both mean asked a question / asked questions.

With many suru-nouns like 質問, Japanese often allows both:

• 質問をする
• 質問する

The version with を can sound a bit more explicit because it clearly marks 質問 as the object of する. The version without を is also very natural and common.

So this sentence could also be:

• 研究室で実験をしたあと、教授に質問しました。

It can mean either asked a question or asked questions, depending on context.

Japanese nouns usually do not show singular vs. plural the way English does. So 質問 by itself does not tell you whether it was one question or several.

You understand it from context.

So:

• 教授に質問をしました could mean:
  • I asked the professor a question
  • I asked the professor questions

They do different jobs in the sentence.

• した is inside the time expression 実験をしたあと = after doing the experiment
• しました is the main verb of the whole sentence = asked

Both are past because the whole sentence describes completed actions in the past.

Also notice the style difference:

• した is plain form
• しました is polite form

This mixture is normal in Japanese. In subordinate parts like Vたあと, Japanese often uses the plain form even when the main sentence is polite.

So this is completely natural:

• 実験をしたあと、教授に質問をしました。

Yes, very normal.

The main sentence ends politely with しました, but grammar patterns inside the sentence often require the plain form.

Here:

• したあと uses the plain past form because that is how the grammar works
• 質問をしました is the polite main predicate

This happens a lot:

• ご飯を食べたあと、出かけました。
• 宿題が終わったら、寝ます。
• 日本に来てから、日本語を勉強しています。

So even though English learners sometimes expect the whole sentence to stay in one style, Japanese commonly uses plain forms inside dependent clauses.

A natural reading is:

けんきゅうしつ で じっけん を した あと、きょうじゅ に しつもん を しました。

Word readings:

• 研究室 = けんきゅうしつ
• 実験 = じっけん
• 教授 = きょうじゅ
• 質問 = しつもん

Not always.

研究室 literally means research room or laboratory, but in Japanese it can also refer to a professor’s lab, research group, or academic office/lab space, especially in a university setting.

So depending on context, 研究室で could mean:

• in the laboratory
• in the research lab
• in the professor’s lab
• in the research office/group’s room

If the sentence also has 実験, then laboratory/lab is especially natural.

Yes, Japanese word order is fairly flexible as long as the particles make the roles clear.

For example, these are also possible:

• 実験を研究室でしたあと、教授に質問をしました。
• 教授に、研究室で実験をしたあと、質問をしました。

However, the original order is very natural and easy to understand:

• 研究室で実験をしたあと、教授に質問をしました。

Japanese often puts the background or time-setting information first, then the main action at the end.

The basic structure is:

• [研究室で実験をしたあと]、[教授に質問をしました]

So it breaks into:

1. 研究室で実験をしたあと
   = after doing an experiment in the lab

2. 教授に質問をしました
   = asked the professor a question / questions

The first part sets the time/order, and the second part gives the main action.

Yes.

With a noun, you usually use:

• Nのあと(で) = after N

Examples:

• 授業のあとで = after class
• 昼ご飯のあとで = after lunch

With a verb, you use:

• Vたあと(で) = after doing V

Examples:

• 食べたあとで = after eating
• 読んだあとで = after reading

In your sentence, it is the verb pattern:

• 実験をしたあと

If you wanted a noun version, you might say something like:

• 実験のあと、教授に質問をしました。

That would mean After the experiment, I asked the professor a question / questions.