下面的程序是位掩码技术实现权限的组合管理。首先定义四个权限常量，分别对应读、写、修改、删除， 每个权限占用整数的一个独立二进制位。初始化权限掩码 mask 为 0，代表没有任何权限。如果想实现如下的操 作：添加读权限；添加写权限；清除读权限，其他位不变；添加删除权限。则横线处应该填入的是（　　）。

#include <iostream>
using namespace std;

int main() {
    const int READ = 1 << 0;
    const int WRITE = 1 << 1;
    const int MODIFY = 1 << 2;
    const int DELETE_ = 1 << 3;
    int mask = 0;
    __________________________
    return 0;
}

{{ select(1) }}

• mask = mask | READ;
  mask = mask | WRITE;
  mask = mask & (~READ);
  mask = mask | DELETE_;
  

• mask = mask & READ;
  mask = mask & WRITE;
  mask = mask | (~READ);
  mask = mask & DELETE_;
  

• mask = mask | READ;
  mask = mask & WRITE;
  mask = mask & (~READ);
  mask = mask | DELETE_;
  

• mask = mask | READ;
  mask = mask | WRITE;
  mask = mask | (~READ);
  mask = mask | DELETE_;