小雨原来有16本书,借给小兰7本。小雨还有多少本书?
16 - 7=9(本)
He has passed the examination ____ his hard work. [ ]
A. because
B. because of
C. thank to
D. as a result
人群作为一个整体对传染病的易感程度,称()。
A.感染力
B.致病力
C.传染力
D.人群易感性
E.疫区