Miss Richards was a teacher at a school for boys and girls．She________chemistry and physics from the lowest to the highest classes in the_______．Sometimes students________them rapidly，but sometimes they were very________，and then Miss Richards had to________things many times．
One year，the first class had been studying chemistry for several________when Miss Richards suddenly asked，“What is water？Who knows？________up？”
There was silence(沉默)for a few seconds，and Miss Richards felt sad(难过的)，but then one boy_______his hand．
“Yes，Dick？”said Miss Richards encouragingly(鼓励地)．He was not one of the brightest children in the class，so she was________that he could answer．
“Water is a liquid which has no______until you wash your hands in it，Miss．Then it turns black，”the boy replied with great confidence(信心)．

A．teaches B．teaching C．taught D．teach

A．schooling B．school C．class D．home

A．learned B．learning C．had been learned D．were learned

A．slow B．being slow C．slowly D．slowest

A．repeated B．repeating C．repeats D．repeat

A．years B．minutes C．weeks D．seconds

A．Put B．Hands C．Get D．Look

A．lowed B．rode C．raised D．put

A．sad B．glad C．angry D．hungry

A．color B．colorful C．colorless D．with color