🅐 cout << 'They\ 're planning a party for their friend'\s birthday." << endl;   🅑 cout << "They\ 're planning a party for their friend 's birthday. '<< endl;    🅒 cout << 'They 're planning a party for their friend 's birthday. '<< endl; 🅓 cout << "They\ 're planning a party for their friend\ 's birthday." << endl;