1. Everyone (make) __________________ contributions for the past few weeks. 2. How many wars do you think there (be) _______________ in the history of mankind? 3. Nearly three-fourths of the surface of the earth (be) __________________ covered by water. 4. Recently there (be) __________________ times when I have seriously thought about my future career.

1 has made.

`-` for the past few weeks: HTHT.

`=>` S + have/has + Vpp + O.

2 were.

`-` In the history of mankind: Quá khứ đơn.

`=>` S + was/were + O.

3 is.

`-` ''nearly three-fourths of the surface of the earth'' là số ít.

`=>` Dùng tobe ''is'' .

4 has been.

`-` recently: HTHT.

`=>` S + have/has + Vpp + O.

`1` has made

`-` HTHT, dấu hiệu: for the past few weeks

`->` S + have/has + VpII + (by O)

`-` "everyone" là đại từ bất định, đại từ bất định luôn đi với số ít.

`2` were

`-` QKĐ, dấu hiệu: in the history of mankind

`->` S + was/were

`-` Có "How many wars" `->` đi với tobe "were"

`3` is

`-` Sự thật hiển nhiên `->` HTĐ

`->` S + am/is/are

`-` "nearly three `-` frouths of the surface of the earth" là số ít `->` đi với tobe "is"

`4` has been

`-` HTHT, dấu hiệu: recently

`->` S + have/has + VpII