There is reason to believe that most writers have difficulty in ________ the opening paragraphs of

their papers.    [ ]

A. constituting      

B. constructing      

C. comprising      

D. founding

某某同学家因自来水笼头关不紧，造成滴水，这位同学是个有心人，他抽空做了测算，测得每天大约滴16千克的水，照这样计算一年（按365天计算）要浪费______千克水．如果把这些水分别装在饮水桶内（每桶约重19千克），算算大约能装______桶，你家每月喝______桶，算算这些水够你家喝______个月．合______年．通过测算所得的这组数据，你有什么想法？