Higher education is very importance to national economies, and it is also a source of trained and educated personnel for the whole country.

A. The Queen Elizabeth is the largest ship to be built on the Clyde.

B. The Queen Elizabeth is the largest ship to build on the Clyde.

C. The Queen Elizabeth is the largest ship built on the Clyde.

D. The Queen Elizabeth is the largest ship buliding on the Clyde.

A. I have been writing this essay for hours and it's still not right.

B. It's hours ago since I last wrote this essay correctly.

C. The last time I started writing this essay was hours ago, which is still not right.

D. I didn't stop to write this essay hours ago and it's still not right.

A. diverse

B. diversify

C. diversely

D. diversity

A. middle

B. main

C. landscape

D. point

A. 36

B. 12

C. 15

D. 20

A. being lived

B. living

C. to live

D. lived

A. atmosphere

B. carbon footprint

C. ecosystem

D. famine