Most television viewers don't remember ______ they hear after they listen to the weather report. [ ]

A. that

B. which

C. what

D. whether

阅读和理解下面程序段：
class Manager extends Employee
public Manager(String n，double s，int year，int month，int day)
super(n，s，year，month，day)；
bonus=0；

public double getSalary()
double baseSalary-super．gerSalary()；
return baseSalary+bonus；

public void setBonus(double b)bonus=b； )
private double bonus；

Manager是Employee的子类，其理由是( )。