A:产前诊断
B:近亲结婚
C:高龄生育
D:早婚早育
I was looking for a birthday gift for my mother, but I couldn't find ______ suitable.
①无限小数是无理数; ②无理数是无限小数;
③无理数的平方一定是无理数; ④实数与数轴上的点是一一对应的.
正确的个数是( )