32. Tens of thousands of trees _____ in the area in the past few years.

A．have been planted

B．were planted

C．have planted

D．had planted

在家庭电路中，空调与其它用电器的电路连接方式为______联（选填“串”或“并”），它正常工作的电压约为______伏，若该空调标有“2kW”的字样，则它连续正常工作5小时，耗电______度．