一小船相对地面以速度v₁向东匀速行驶，若在船上以相对于地面的速率v水平向西抛出一个质量为m的重物，则小船的速度将（　　）

A．不变

B．增大

C．减小

D．改变方向

—Let's go to find our manager in his office.

—It's so late at night. He _____ be there . Let's make it another day.[ ]

A. can't  

B. needn't  

C. mustn't  

D. ought not to have been