So the idea that the gas man can turn up at my mom's door and he can show my mom his phone, and she can tap it with her phone, and it will come up with green if he really is from British Gas and allowed in, and it'll come up with red if he isn't, end of story.
所以当天然气工人 出现在我母亲的门口， 他出示他的手机， 我母亲点一下自己的手机， 就可以知道他是不是 来自英国天然气公司， 可不可以让他进来。 如果他不是，就会出现红叉。 就这么简单。