下列描述主动脉瓣二瓣化畸形，错误的是（）。

A.主动脉瓣开放面积减小

B.左心室壁增厚

C.左心室壁运动幅度减弱

D.主动脉瓣叶回声增强

E.CDFI示主动脉瓣收缩期前向血流呈五彩镶嵌色

All passengers ______, please fasten your seat belts and remain seated ______ the plane is landing.

A．on board; before

B．abroad; since

C．on the board; after

D．aboard; when