If a member is made from segments having thin walls under internal shear force, only the shear flow ( ) to the walls of the member is important. The shear flow varies ( ) along segments that are ( ) the direction of the shear force V.
选项：

A:parallel to, linear, perpendicular to
B:perpendicular to, linear, parallel to
C:parallel to, parabolically, perpendicular to
D:perpendicular to, parabolically, parallel to