题干
You'd better ask a ______, such as your aunt or sister, to look after your children while you are away.
A：classmate
B：neighbor
C：relative
答案(点此获取答案解析）
C
You'd better ask a ______, such as your aunt or sister, to look after your children while you are away.
A：classmate
B：neighbor
C：relative
固体配制溶液时，为了得到澄清溶液并防止变质，常向溶液中加入少量R的单质和盐酸。已知
有5个电子层，其最外层有2个电子，则下列推断正确的是