Prefix is a word, letter, or number placed before another.
suffix is a morpheme added at the end of a word to form a derivative.
Please show us the list you're referring to.
If you want to use consistent verb tenses in telling a story, that means you have to use the same tense, or at least they all should be in the past/present/future, depending on the first verb in the sentence. Here, the correct answer is:
B) I met Rob for the first time in the school infirmary, and he smiled at me even though he was clearly in pain.
