—No , you ________. It is not as serious as the one we went to last week .
A:mustn't
B:needn't
C:can't
D:wouldn't
现在是 ____ 时半
再过2小时是____时半
如图,以直角三角形a、b、c为边,向外作等边三角形,半圆,等腰直角三角形和正方形,上述四种情况的面积关系满足S1+S2=S3图形个数有( )
规范的操作是实验成功的关键.下列实验操作正确的是( )