My son is more careful with his lessons than before and makes ________ mistakes in his exercises.

[　　]

The foreigners have visited many places of interest ________ the west of China.

[　　]

China became a WTO member ________ December 11^th, 2001.

[　　]

Long long ago, people didn't know the earth ________ round the sun.

[　　]

Have you ever ________ Lin Tong to see the Terra Cotta Warriors?

Many of us ________ there every year.

[　　]

If it ________ fine tomorrow, I won't go there.

[　　]

She ________ the River Park three times.

[　　]

Have you ever ________ to the USA?

[　　]

The students _______ a biology class when the visitors came.

[　　]

A. had

B. were having

C. will have