(2013·德州期末校际联考) an hour every day has made a considerable difference to my health.
A. Having walked
B. Walk
C. Walking
D. Walked
网友回答
A. Having walked
B. Walk
(答案→)C. Walking
D. Walked
解析：句意：每天步行一小时极大地改善了我的健康(状况)。分析句子结构可知，本句话缺少主语，只有v.ing短语可以作主语，故可排除B、D；且“每天走路一小时”是一种经常性的动作，故排除A。C项正确。