单选题 One of the responsibilities of the Coast Guard is to make sure that all ships ______ follow traffic roles in busy harbors．
A．cautiously B．dutifully C．faithfully D．skillfully

【正确答案】 B
【答案解析】[解析] dutifully“守本分地”。A．cautiously“小心谨慎地”；C．faithfully“忠诚地”；D．skillfully“熟练地”。