— I didn't hear you come in last night.      

— That's good. We tried ______ noisy. [ ]

A. not be

B. not to be

C. to be

D. to be not

如图所示，潜水艇正在下潜，当潜水艇潜入水面以下继续下潜的过程中，潜水艇所受的浮力将

A．变大

B．变小

C．不变

D．无法确定