The Correct Answer: Option 'A' makes more sense.

Explanation:
The sentence "The students stopped talking when the teacher walked into the room" makes more sense because it accurately reflects the sequence of events and the cause-and-effect relationship between the actions of the students and the entrance of the teacher.

Reasons why Option 'A' is correct:
- Verb Tense Agreement: In the sentence "The students stopped talking when the teacher walked into the room," both verbs 'stopped' and 'walked' are in the past tense, which indicates that the actions took place in the past. This tense agreement ensures grammatical correctness and clarity in the sentence.
- Cause-and-Effect Relationship: The use of the word 'when' in the sentence establishes a cause-and-effect relationship between the actions of the students and the entrance of the teacher. It implies that the students stopped talking because the teacher walked into the room, which is a logical sequence of events.
- Clarity and Coherence: The sentence is clear and coherent, allowing the reader to easily understand the intended meaning. The action of the students stopping talking is directly attributed to the teacher's entrance, making the cause-and-effect relationship clear.

Reasons why Option 'B' is incorrect:
- Verb Tense Inconsistency: In the sentence "The students were stopping talking when the teacher walked into the room," there is a tense inconsistency. The use of the past continuous tense 'were stopping' suggests an ongoing action, but it contradicts the fact that the students actually stopped talking when the teacher entered the room.
- Illogical Sequence: The use of the past continuous tense in option 'B' implies that the students were in the process of stopping talking when the teacher walked into the room. However, it is more logical to assume that the students had already stopped talking by the time the teacher entered, as indicated in option 'A'.

Therefore, option 'A' is the correct sentence as it accurately conveys the intended meaning, maintains tense agreement, and establishes a clear cause-and-effect relationship between the actions of the students and the entrance of the teacher.