Goldfish don't know _______ to them three seconds ago.
A:what happens
B:what is happening
C:what happen
D:what happened
如图所示,两个实心正方体A、B放在相同的海绵上,海绵的凹陷程度如图所示,已知A、B正方体的边长hA>hB,下列判断正确的是( )