My C++ Quiz

Question #63: Which lines below should not compile?
58% on 1004 times asked

1 struct A
2 {
3    A(int x) : n(x) {}
4    int n;
5 };
6
7 int main(int argc, char** argv)
8 {
9    A a1;
10   A a2(2);
11   A a3(a2);
12   return 0;
13 }