Explanation:
Let's break it down carefully:

The sentence says the lecturer "had to walk out" — meaning the noise was happening while he was still there.
So we need a tense that shows an action in progress in the past (not just completed).

Now the options:
- A. made — simple past, shows a completed action (but here, the noise was ongoing).
- B. had been making — past perfect continuous, suggests they had been making noise *before* the lecturer arrived (not best fit here).
- C. were making — past continuous — shows the action was ongoing while the lecturer walked out (perfect fit!).
- D. had made — past perfect, shows a completed action before another past event (doesn't fit well here).
- E. would have been making — conditional past, totally wrong here.

Therefore, the correct answer is C. were making.

Full sentence:
The students *were making* so much noise while the lecturer had to walk out of the class.

Would you like me to also give you a simple "past continuous" formula you can memorize for these questions?