冻疮发病的主要机体因素为()
A.手足多汗
B.末梢循环较差
C.鞋袜过紧
D.缺乏运动
参考答案:B
Tom doesn’t want to take part in any school activities,________.
A.and David doesn’t too
B.and David doesn’t either
C.and so doesn’t David
D.and either does David
如图所示,电磁铁附近的小磁针处于静止状态,则电磁铁的A端是______极,当滑动变阻器的滑片向b端滑动时,电磁铁的磁性将______.