单选题 Though Mary continued working, she kept looking at the clock ______, thinking of her sick baby in hospital.
[A] all the time [B] at once [C] after a while [D] for a moment

【正确答案】 A

【答案解析】[解析] 本题考查副词短语的用法。句意为“虽然Mary继续工作着，可她一直看着钟，担心着她生病住院的孩子。”all the time正好表达了“一直”的含义；at once“立刻，马上”：after a while“过一会儿”；for a moment的意思是“一会儿”。