单选题
With three young children to take care of, Cathy is kept on the run every minute of the day.
A. walking B. at full speed C. busy D. on foot
【正确答案】
C
【答案解析】[解析] 句意是：由于有三个孩子需要照料，凯茜时时刻刻都在忙碌。on the run意思为“活动，忙碌”。walk“走路”；at full speed“以最快速度”；busy“繁忙的”；on foot“步行，在进行中”。根据句意可推断出正确答案是C选项。