I promised Li Ming I would keep the secret to . （我自己）
Jack enjoys and sunbathing with his friends. （游泳）
There are many online libraries where you can read books for ________, such as the national Online libraries Library of China and Shanghai Library. （免费的）
The app about how to learn Chinese is very popular ________ the foreigners.（在……当中）
Jumping the rope is a kind of full-body exercise and it is great for the ________（大脑）.