在平行四边形、菱形、矩形、正方形、圆中，既是中心对称图形又是轴对称图形的图形个数为（ ）
A：1
B：2
C：3
D：4
A single-parent child should have the right to enjoy normal parental love from both just as his other peers, which some psychologists see as _____to their emotional well-being.
—These pears look ．
—Yes．Let's get some．We haven't got any at home．
