Five years ago the population of the village was 2000.Now it’s 1500,which means that it’s

decreased       25%.[ ]

A.to

B.from

C.by

D.for

判断人工呼吸是否有效，主要观察（）

A.吹人气量是否足够

B.口唇发绀是否改善

C.胸廓是否起伏

D.瞳孔是否缩小

E.心跳是否恢复