根据下列物质的名称，就能确认是纯净物的是（） A．二氯甲烷 B．三溴乙烷 C．已

具有补血养阴、填精益髓功效，为补血要药的药物是（）。

A.当归

B.熟地黄

C.何首乌

D.白芍

E.阿胶

短文改错（共10小题；每小题1分，满分10分）

Last week I went to visit to my former neighbor, Mr. Yang. He and I used to living next to each other for many years. About half a year ago, the old building , that we were living in , were going to be pulled down to make room for a main street. So I had to move apart. Mr. Yang now lives in the suburbs near a beautiful park. His new apartment is much big than before. The only problem is that it took quite a long time to get to the downtown area. Therefore, Mr. Yang doesn’t seem to worry about the long distance. He says that new subway line is to be built in a few year and he is sure life will be better in the future.

以社会救助为（）层、社会保险为（）层，积极构建以企业（职业）年金等补充社会保险和商业保险为补充层的多层次社会保障体系，进一步突出对弱势群体的保障和救助功能，保障其生存质量和健康水平，提供弱势群体发展的必要基础。

A.发展、保底

B.主体、保底

C.保底、主体

D.保底、发展

心尖部第一心音增强的是（）

A.肺心病

B.心肌炎

C.主动瓣关闭不全

D.二尖瓣狭窄

E.二尖瓣关闭不全

溶冰观测的目的是使湿球上的纱布的冰溶化，以保持良好的水面蒸发状态。（）