天津历史上发生过海陆变迁的有力证据是[ ]
A.天津沿海盛产海盐
B.大港、汉沽等区县有分布很广的贝壳堤
C.天津地势北高南低
D.天津地区地热资源丰富
答案:B
下列物质中,摩尔质量最大的是
A.10mlH2O
B.0.8molH2SO4
C.54gAl
D.1gCaCO3
—What have you done ______ the nuts?
—We've given them to Polly. [ ]
A. to
B. for
C. at
D. with