继承时有关构造函数要注意的一些问题

//继承时有关构造函数要注意的一些问题
#include <iostream>
using std::cout;
using std::endl;

class Base
{
public:
Base(){}
Base(int n){}
};

class C_A1: public Base
{
public:
C_A1(){}
C_A1(int n0,int n1):Base(n0){}
};

class C_A0: public Base
{
public:
C_A0(){}
C_A0(int n0,int n1):Base(n0){}
};

class C_B0: public C_A0,public C_A1
{
public:
C_B0(){}; //若定义了此默认构造函数，则它的基类要定义默认构造函数,若未定义
//此默认构造函数，则它的基类默认构造函数可有可无
C_B0(int n,int n0,int n1,int n2):C_A0(n,n1),C_A1(n0,n2)
{

}
};

int main()
{
return 0;
}

若将上述代码中的C_B0(){}除去，编译时将出现如下的错误
testcpp.cpp: In constructor 'C_B0::C_B0()':
testcpp.cpp:201:15: error: no matching function for call to 'C_A0::C_A0()'
testcpp.cpp:201:15: note: candidates are:
testcpp.cpp:195:9: note: C_A0::C_A0(int, int)
testcpp.cpp:195:9: note: candidate expects 2 arguments, 0 provided
testcpp.cpp:191:7: note: C_A0::C_A0(const C_A0&)
testcpp.cpp:191:7: note: candidate expects 1 argument, 0 provided
编译失败。