What is implied hut not directly stated in the passage is that ________.

A．young people have been the leaders in the fight against authority

B．today, jeans are no longer looked down upon

C．jeans are the typical dress of civil rights marchers

D．formerly students were not allowed to wear jeans to class

从事顶推的机动船在航不对水移动时应显示（）.

A.左右舷灯

B.用两盏桅灯代替前桅灯或后桅灯

C.尾灯

D.舷灯，尾灯，并用两盏桅灯代替前桅灯或后桅灯