The sentence uses the word 'were making' indicative of past continuous tense. So, the most appropriate answer is the one that shows something was being done by students( i. e making noise).

Option A) is incorrect because it says the noise 'is being made' which is in the present continuous tense. Option B) is incorrect because it is in the past perfect tense. Option C) is in the simple present tense. So, the correct answer is D) noise was being made in the classroom by the students.