信号发出后如有紧急情况,可随时发出()信号。
A.下放
B.停车
C.提升
参考答案:B
两个不完全相同的梯形一定不能拼成一个平行四边形.______.
All the others seemed to know each other and I began to feel .
A.given away
B.fallen behind
C.turned down
D.left out