急性肺动脉栓塞最常发生于
A．肺心病B．长期卧床性疾病C．肺动脉瓣关闭不全D．肺结核病E．肺动脉狭窄
参考答案：B
.When we reached the station, the train had still not arrived; so we ______.
a. needed not to hurry b. needn’t have hurried
c. need not to have hurried d. didn’t need to hurry
根据电器的执行功能分类（）。
A、有触点电器
B、无触点电器
C、自动电器
D、混合式电器
