胸膜摩擦音听诊的时相特点为
A．吸气初期B．吸气中期C．吸气末期D．呼气期E．呼吸两相
参考答案：E
线圈的功率损耗是正常工作时电流值的（）与它的匝数的乘积。
A.1／2倍
B.两倍
C.平方
D.立方
We need to have factual knowledge ( ) our marketing strategy.
A．on which to base
B．which to base upon
C．to which base
D．and based on
