题干
Among the 15-year-old children, some studying in university while others are still learning to read and write.
A：should have bee
B：would have bee
C：can be
D：must be
答案(点此获取答案解析）
C
子排布式如下：①1s22s22p63s23p4；②1s22s22p63s23p3；③1s22s22p5，则下列有关比较中正确的是