19.動力船舶從事拖曳作業，如拖曳長度，超過二百公尺時，應顯示號標為何？
(A)一個球形
(B)一個菱形
(C)二個球形
(D)球形－菱形－球形，三個上下垂直

AS per Rule 27 Vessels not under command or restricted in their ability to manoeuvre
(iii). when making way through the water, a masthead light or lights, sidelights and a sternlight, in addition to the lights prescribed in sub-paragraph (i);

(b). A vessel restricted in her ability to manoeuvre, except a vessel engaged in mine clearance operations, shall exhibit:
(i). three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;
(ii). three shapes in a vertical line where they can best be seen. The highest and lowest of these shapes shall be balls and the middle one a diamond;  

D去爭取 也有機會的rule23 並無取代rule 27