Ex 1 :

1 . do you look

2 . have been

3 . was looking

4 . will be

5 . started

Ex 2 :

1 . I haven't eaten this kind of food before 

2 . Those plants were built 20 years ago

3 . The streets haven't been cleaned for a week

4 . The sea was too rough that the children couldn't go swimming

1.are you looking

2.have been

3.was looking

4.will be(điều kiện loại 1)

5.started(10 years ago->QKD)

Ex 2:

1.I haven't eaten this kind of food before.

2.Those plants were built 20 years ago.(by them bỏ)

3.The streets haven't been cleaned for a week.(by them bỏ)

4.The sea was too rough for the children for the children to swim.(too+adj(+for O)+to V:Quá (cho ai)để làm gì)