完形填空
Miss Richards was a teacher at a school for boys and girls. She __1 chemistry and physics from the lowest to the highest classes in the __2 . Sometimes the new classes 3 rapidly, but sometimes they were very 4 , and then Miss Richards had to 5 things many times.
One year, the first class had been studying chemistry for several __6_ w hen Miss Richards suddenly asked, "What is water? Who knows? 7__ up?"
There was silence (沉默) for a few seconds, and Miss Richards felt sad (难过), but then one boy 8 his hand.
