Answer:
C. Sentence 3
Step-by-step explanation:
All of the other sentences are written in past tense. I know this because the author used words such as "started", "posted", and "answered". However, the third sentence uses the word "will" which indicates something has not been done yet, it will be don in the future. Since this does not match the rest of the sentences, it is incorrect.
Incorrect Sentence:
Many friends will write comments to us.
Correct Sentence:
Many friends wrote comments to us.