氧化态的铁催化剂对氨合成反应没有活性，因此使用前必须将其还原成金属（）。
A.Fe2O3
B.a-Fe
C.铁离子
D.Fe
参考答案：B
婴儿最理想的天然食品是
A．母乳
B．羊乳
C．黄豆制品
D．牛乳
E．全脂奶粉
Grace doesn't want to move to New York because she thinks if she ________ there, she wouldn't
be able to see her parents very often. [ ]
A. lives
B. would live
C. has lived
D. were to live
