12. A vessel is seen showing three shapes in a vertical line; the top and bottom ones are black balls and the middle one is a black diamond. What does this daytime signal indicate?
(A) It is a vessel engaged in dredging.
(B) It is a vessel restricted in her ability to manoeuvre.
(C) It is a vessel at anchor.
(D) It is a vessel engaged in a mine clearance operation.

答案：登入後查看
統計： A(0), B(1), C(0), D(0), E(0) #3899947