They (clean) the beach one week ago

1) They (clean) the beach one week ago
2) They (collect)hundreds of books so far
3) I (collect) stamps when i was a child
4)She (fly) to Da Nang many times but last year she (go) there by train
5) you ever (see) a real lion? No ,but i (see) a real elephant when we went to the zoo last month