Choose the correct form of the verb:
3. James (learned / is learning / has learned) English at school.
4. They (had sailed / sail / had been sailing) along the shore before being rescued.
5. We (take / took / are taking) French classes twice a week this year.
6. Ann (were writing / was writing / are writing) a beautiful letter when you arrived.
7. They (visited / have visited / are visited) London twice.