It is B), because A) would work if it didn't start with "when". What happened when she went to the store to get groceries? Well the sentence doesn't tell us, and it is missing its complete predicate. It only gives us HALF a predicate, leaving out a verb phrase. Answer C) doesn't have a complete verb phrase, either. Garbage is most likely the subject, but it should have a linking verb like is, was, or will be. D) is missing a subject. It does not tell us WHO or WHAT cleans up after the storm. However, B) has everything needed. The subject is a pronoun, which is "It". The predicate is "was a good day for ice cream", with the verb phrase being "was a good". Was is the linking verb between it and a good day (for ice cream, that is).
God Bless.
Hope It Helped.
