转子灭磁能量的单位是（）。
A、A
B、V
C、W
D、J
参考答案：D
The Harry Potter books are quite popular; they are in great ___ in this city. [ ]
A. quality
B. progress
C. production
D. demand
居住区内绿地分为( )类。
A．三
B．五
C．六
D．四
