(2013·安徽省芜湖三校一模)A recent study has found that the number of smokers sharply over the past five years.
A. is increasing
B. are increasing
C. has been increasing
D. have been increasing
网友回答
A. is increasing
B. are increasing
(答案→)C. has been increasing
D. have been increasing
解析：选C 考查时态和主谓一致。句意：最近一项研究表明，在过去五年里，吸烟者人数急剧上升。the number of后接复数名词作主语，谓语动词则用第三人称单数；时间状语over the past five years表明用现在完成进行时。