It . . . . . . . . a nice day; therefore, we went swimming.

was
had been
has been
used to be E. would be

The correct answer is A. was.

The sentence is in the past tense, so the verb must also be in the past tense. The other options are not in the past tense.

  • B. had been is in the past perfect tense, which is used to talk about something that happened before another event in the past.
  • C. has been is in the present perfect tense, which is used to talk about something that started in the past and continues to the present.
  • D. used to be is in the past simple tense, which is used to talk about something that happened regularly in the past but does not happen anymore.
  • E. would be is in the conditional tense, which is used to talk about something that might or could happen in the future.

In this case, the sentence is talking about a specific day that was nice, so the past tense is the most appropriate tense to use.