1a Look at sentences a-d and choose the correct alternatives in 1 and 2.

1a

1. We use the present perfect/past simple for actions or experiences which happened at a specific moment in the past, or actions which started and finished in the past.

2. We use the present perfect/past simple for actions or experiences which happened at an unspecified moment in the past, actions which started in the past and continue to the present, or past actions which have a result in the present.