A vessel，which does not normally engage in towing operations，is towing a vessel in distres

A vessel，which does not normally engage in towing operations，is towing a vessel in distress.She ____.

A.need not show the lights for a vessel engaged in towing，if it is impractical to do so

B.may show the lights for a vessel not under command

C.must show a yellow light above the stern light

D.must show the lights for a vessel towing

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