声音的传播需要______.______、______、______可以传播声音.
声音的传播需要介质,一切的固体、液体和气体都可以传播声音.
故答案是:介质;固体;液体;气体.
----- Mum, I think I’m __________ to get back to school .
----- Not really , my dear. You’d better stay at home for another day or two.
A.so well
B.so good
C.well enough
D.enough well
已知直角三角形两条较长边的长分别为8和6,则斜边上的中线为 _________ .