Present perfect and past perfect tense.надо изменить предложения.1.nick (do) his homework by his 7 o'clock.you ever (see) the pyramids? this little boy never (see) crocodiles.when i(come) to the station yesterday,i (learn) that my train already ( leave)

1.Nick has done his homework by his 7 o'clock.2. Have you ever seen the Pyramids? 3. This little boy has never seen crocodiles. 4. When I came to the station yesterday, I had learned that my train has already left.