原子结构的第三壳层最多容纳电子数是()
A.2个
B.8个
C.18个
D.32个
E.50个
参考答案:C
You are given only half an hour to finish your speech on the subject, so you'd better not _____ it too far. [ ]
A. expand
B. extend
C. enlarge
D. increase
4个月男孩,冬季出生;足月顺产,单纯牛奶喂养,近10天来烦躁,多汗,夜间睡眠不好。
首先考虑的诊断()
A.佝偻病
B.缺铁
C.缺锌
D.血磷高
E.维生素A缺乏