Обьясните пож почему презен симл или презен сонтиниюс

1. I tried to phone you yesterday afternoon. Sorry,Greg, I was not at home. I was helping Chris to prepare a survey on school life in the UK.
2. When John arrived, we were having breakfast.
3. Why you didn't you do your homework yesterday? I was visiting my grandma in hospital.
4. What was happening in this room when you walked in today?
5. What toy did you do last weekend?
6. While I was surfing the net yesterday, I found a really interesting website.
7. No one could see the puppy because it was hiding in the rose bushes.
8. I didn't hear the thunder during the storm last night because I was sleeping.

9. Jack was walking down the street when it began to rain.
10. At eight o'clock last night my little brother was sleeping happily.
11. While Evans was telling her grandson a fairy tale, the little boy fell asleep,so she closed the book and quietly left the room.
12. What Lizzy was wearing at the party last night?
13. My cousins were quarrelling about something when I came into the room.
14. It was early morning. The sea was sparkling under the rays of the sun. The birds were singing their beautiful songs.