硫和磷都是钢铁材料的有害元素,它们分别使钢材具有(),冷脆性。
参考答案:热脆性
—Let's go climbing the mountains if it ______ this weekend.
—But nobody knows if it ______. [ ]
A. is fine; will rain
B. will be fine; rains
C. will be fine; will rain
D. is fine; rains
可促进小肠对钙的吸收的是()
A.维生素A
B.维生素B
C.维生素C
D.维生素D3
E.维生素E