2. Are they listening to music now? - No, they are warching the new movie.
3. The children are playing the game now. They play it all the time.
4. Leo Fender invented the first electric guitar in 1950.
5. He felt pity when he blew up a bus full of people.
6. Kirk wrote this beautiful poem when he was having holidays.
7. I had completed the last level of the game by 10 o'clock last Wednesday.
8. He had told me the solution to this probem before I found it out myself.
9. Jack will find a new job someday. He will begin looking for it tomorrow morning.
10. If I know something about it, I will onform you about it as soon as possible.
11. He will paint a portrait at this time tomorrow.
12. We will have passed pass all the exams by June 2018.
13. The builders will have demolished the school by the beginning of September.
14. I will have written the report by the time the secretary arrives.
15. Children don't like porridge. They preffer something sweet and tasty.

in the hospital - то же значение, американский вариант
at the hospital - в какой-то больнице, акцент на учреждение
Источник - Collins Cobuild English Usage