一般电除尘多为负电晕，其收尘效率高，可到98%~99%，改为正电时效率只有（）左右。
A.70%
B.80%
C.90%
D.85%
参考答案：A
More highways have been built in China,___________it much easier for people to trave form one place to another.
A．making
B．made
C．to make
D．having made
- Grandpa has changed a lot.
- So he has. He spends more time than he used to ______ games
with the children.
A．play
B．playing
C．played
D．plays
