【正确答案】 B

【答案解析】[解析] at once：马上。immediately：马上。如：It's getting late. We must go back home immediately. 天晚了，我们得马上回家。soon：很快。We'll have lunch soon. 我们很快就要吃午饭了。now：现在。If we leave now we'll be there before dark.如果我们现在离开，天黑前就能到那里。early：早。Mary gets up very early.玛丽起得很早。