Answer:
The pair of sentences that is written correctly without sentence fragments is the following one:
1. A. Helen took the fish out of the oven. It was cooked perfectly.
2. A. We arrived too late, and the bowling lanes were all taken.
Explanation:
1. A. Helen took the fish out of the oven. It was cooked perfectly.
"Helen" is the subject in the first clause, and the verb is "took".
"It", referring to the antecedent "the fish", is the subject in the second clause, whose main verb is "cooked", which is in passive voice ("was cooked").
2. A. We arrived too late, and the bowling lanes were all taken.
"We" is the subject in the first clause, and the verb is "arrived".
"The bowling lanes" is the subject in the second clause, whose main verb is "taken", which is in passive voice ("were taken").