55[823]The material used extensively as electrolytic protection around bronze

propellers is ______.

A. Brass

B. Copper

C. Lead

D. Zinc

56[3560]Before starting any diesel or gasoline engine，which of the following

must be checked?

A. Oil level

B. Flow of cooling water

C. Exhaust discharge

D. All of the above

57[5295]The holding capability of an anchor is primarily determined by the

______.

A. shape of the anchor

B. stowage of the anchor on board

C. anchor's ability to dig in

D. size of the vessel and its draft

58. A Racon can help with _D_?A.measuring the distance B.measuring the relative C.identifying centimeters D.identifying a seamark

59. [3872]The radio waves used for radar are very short，only ______ long．

A. a few centimeters

B. a few fathoms

C. a few meters

D. a few feet

60. 103. What type of radar can activate a racon?