We brought young children aged 2-4 into our Minds in Development Lab at USC. Each child sat down with an adult who covered her own eyes or ears. We then asked the child if she could see or hear the adult. Surprisingly, children replied that they couldn’t. The same thing happened when the adult covered her own mouth: Now children said that they couldn’t speak to her.

这是2022高考英语全国卷一完形填空中的一个段落。加粗单词显然是复指前面的children，但为什么前面没有用定冠词呢？