Problems relating to people's livelihood have been the focus of the government, especially ______-Premier

Wen Jiabao included them in his government work report last year.

[      ]

A. when

B. as

C. until

D. since

治疗贫血的关键是促进血红蛋白的合成，下列的物质中影响血红蛋白合成的物质是（）

A.铁离子

B.钙离子

C.氨基酸

D.葡萄糖

E.铅