关于以下C++代码，（    ）行代码会引起编译错误。

#include <iostream>

using namespace std;

class Base {

private:

int a;

protected:

int b;

public:

int c;

Base() : a(1), b(2), c(3) {

}

};

class Derived : public Base {

public:

void show() {

cout << a << endl;

// Line 1

cout << b << endl;

// Line 2

cout << c << endl;

// Line 3

}

};