问题
单项选择题
During the day，a vessel picking up a submarine cable shall carry（）.
A.three shapes，the highest and lowest shall be red balls，and the middle shall be a white diamond
B.two black balls
C.three shapes; the highest and lowest shall be black balls，and the middle shall be a red diamond
D.three shapes; the highest and lowest shall be black balls and the middle shall be a black diamond
答案
参考答案：D
