请你用there is\isn'there are\aren't there was\wasn't there were

1.There is a hospital behind my house.
否定：There isn't a hospital behind my house.
在我家后面（没）有一家医院.
2.There are many students on the playground.
否定：There aren't many students on the playground.
在操场上（没）有很多学生.
3.1）There was a tiger in the forest long long ago.
很久很久以前,在森林里面有一只老虎.
2）There wasn't a book on my table just now.
刚才我桌子上没有书.
4.There were a lot of students in the classroom yesterday.
否定：There weren't a lot of students in the classroom yesterday.
昨天在教室里面（没）有很多学生.