—Much knowledge as well as many abilities _____ from our teachers.

—Yes.We should love and respect our teachers.[ ]

A. are learned  

B. is learned

C. learn  

D. learns

下图是我国海军舰艇赴亚丁湾护航时的情景。护航编队一般采用前后护航而不采用并排护航，这是因为当两船高速并排行驶时，两船之间的流体流速（）压强（），容易发生撞船事故。