A:①②
B:①③
C:②④
D:③④
I've got the message from Mr. Wang that what he has settled down in Canada.
垂直作用在物体____并指向物体的力叫压力,压力可以使物体发生____,物体____上受到的压力叫压强.
澳大利亚是一个环境优美的国家.据此和图回答下列小题.