c++构造调用次序问题，求解答

#include<iostream>
using namespce std;
class B1{
public:
B1(int i){
cout<<"B1"<<i;
}
};
class B2{
public:
B2(int j){
cout<<"B2"<<j;
}
};
class B3{
public:
B3(){
cout<<"B3 @";
}
};
class C:public B2, public B1, public B3{
public:
C(int a, int b, int c, int d):
B1(a),numberB2(d),numberB1(c),B2(b){}
private:
B1 numberB1;
B2 numberB2;
B3 numberB3;
};
int main() {
C obj(1,2,3,4);
return 0;
}#笔试题目##C++工程师#