题目

In order to seek better chances outside their countries, many  young people have gone abroad, left their parents behind with76______no clear idea of when they will return home. Their parents spend77______countless alone days and nights, taking care of themselves, in the          78______hope that someday his children will come back to stay with them.       79______The fact where most of these young people have gone to Europeanized   80______or Americaning societies makes it unlikely that they will hold as        81______tightly to the value of duty as they would have h抛物线y=x2-3x-m2与x轴交点的个数是（　　）A．1个B．2个C．0个D．不能确定