Which of the following class DOES NOT need a copy constructor?(下面所列举的类哪个不需要拷贝构造函数?)

题目

Which of the following class DOES NOT need a copy constructor?(下面所列举的类哪个不需要拷贝构造函数?)
A.A matrix class in which the actual matrix is allocated dynamically within the constructor and is deleted within its destructor.(一个矩阵类：动态分配,对象的建立是利用构造函数,删除是利用析构函数.)
B.A payroll class in which each object is provided with a unique ID.(一个花名册类：每一个对象对照着唯一的ID.)
C.A word class containing a string object and vector object of line and column location pairs.(一个word类,对象是字符串类和模板类.)
D.A library class containing a list of book object.(一个图书馆类：由一系列书籍对象构成.)

答案