问题
单项选择题
It is（）for mariners to combine the SART with a float-free satellite EPIRB.
A.essential
B.compulsory
C.optional
D.inadvisable
答案
参考答案：C
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It is（）for mariners to combine the SART with a float-free satellite EPIRB.
A.essential
B.compulsory
C.optional
D.inadvisable
参考答案：C