A:I am convenient to go there by train.
B:I go there by train at convenience.
C:It is convenient for me to go there by train.
D:It is convenience for me to go there by train.
若物体在运动过程中所受到的合外力不为零,则在运动过程中( )
下列有关生物膜的说法不正确的是( )