为什么只有在返回* this时才调用Copy构造函数？

Class Cents(){  
 int m_val;  
 public:  
  Cents(int x=0){ cout<<"Constructor";}
  Cents(const Cents& src){ cout<<"Copy constructor"}
  Cents Add(int val){m_val=val; return *this}  // --->(1)
 }  
Class Cents(){  
 int m_val;  
 public:  
  Cen