气道闭合压正常值为()
A.-6~-4cmH2O
B.-4~-2cmH2O
C.-2~-0cmH2O
D.0~2cmH2O
E.2~4cmH2O
参考答案:B
A lot of modern teaching equipment which will improve the school conditions to a large extent _______ to ten Hope Schools in South China.
A.were sent
B.was sent
C.have sent
D.had been sent
A.变压器输出端所接电压表的示数为20V
B.变压器的输出功率为200W
C.变压器输出端的交流电的频率为50Hz
D.穿过变压器铁芯的磁通量变化率的最大值为20/n2Wb/s