选词填空
for to at of in
全级共回收废电池多少节？
下列是取出少量固体粉末并装入试管进行加热的过程，各步操作中正确的是（ ）
There is a common saying in China________nothing in the world is difficult for one who sets his mind on it.
This is _________ elephant. _________ elephant is from Africa.
