39. The United States has a ............. of around 250 million.

A. population B. separation C. addition D. introduction

40. Vietnamese people are very ...................

A. friend B. friendless C. friendly D. Friendship

41. We were having dinner ……… the telephone rang.

A. when B. while C. until D. what

42. I …… call you as soon as I come back home.

A. have B. will C. am D. is going