Ответ:

Объяснение:

1. *Are* you *learning* this poem now?

I *have been learning* it by heart for half an hour but I *haven't learned* it yet.

2. We *are* still *translating* this article.

We *have been translating* it since morning but ....

3. How long *have* you *been doing* this work?

I *have been doing* it for an hour but I *haven't done* it yet.