能估计特异危险度的是() |能分析多种不同的暴露因素的是()
A.病例对照研究
B.现况研究
C.定群研究
D.筛检
E.生态学研究
参考答案:A|C
A strong earthquake hit Japan on March 11, _____ thousands of people homeless. [ ]
A. to leave
B. having left
C. left
D. leaving
债券质押式回购交易实行质押库制度。( )