题目内容:
During the day, a dredge will indicate the side on which it is safe to pass by displaying_____.A.two balls in a vertical line
B.two diamonds in a vertical line
C.a single black ball
D.no shape is shown during the day
参考答案:
A.two balls in a vertical line
B.two diamonds in a vertical line
C.a single black ball
D.no shape is shown during the day