如图将鼓轻敲一下，然后再重敲一下，两次敲击发出的声音，发生了变化的是 A．音调

June 25, 2011 _______a very bright night in Nanshan Middle School that will never          

_______from memory. Our school has made great breakthrough in the field of education.

A．see; faded

B．witness; fade

C．saw; fade　　

D．witnessed; faded

两条直线不相交就一定平行．______．

前列腺癌符合( )

A．老年男性，排尿困难
B．血清PSA明显升高
C．两者都有
D．两者都无

试述机车受电弓升起前对机车乘务员有何要求？

我国的分配制度是什么