1. Greenland, _____island in the world, covers over two million square kilometers.

A. it is the largest    B. that is the largest      C. is the largest       D. the largest

2. Helen was much kinder to her youngest son than to the others, _____, of course, made the others envy him.

A. who          B. that             C. what             D. which

3. An awful accident_____, however, occur the other day.

A. does             B. did              C. has to           D. had to