1. When I reach the school grounds there are lots of “good mornings” for me from the boys.______ have walked a long way, sometimes up to two hours, to get to school.

A. And many of whom         B. And many of them

C. Many of whom               D. Many of them

2. The other day I was showing the boys the weekly chemistry experiment when, ______ I knew it, the mixture was bubbling over everywhere!

A. after     B. since     C. before     D. as