— Bob, shall we go and meet our new classmate?
— Sorry, I'm busy now. But you ________ ask David to go with you. He is free.
A:need
B:may
C:would
D:must
某几何体的三视图如图所示,其中俯视图与侧视图是半径均为2的圆,则该几何体的表面积是( )
板块构造学说认为地球表面是由____大板块构成,板块是在不断____的.一般来说,板块的内部地壳比较____,板块与板块交界的地带,地壳比较____,多____和____发生.