When learning Chinese language, foreign students can regard some Chinese materials as free Chinese lesson to improve the reading skills. The following is a complete sentence for students who learn in free Chinese lesson should choose the proper words to fill the blanks. 在此，我想对老年朋友说，如果你的身体 ，可以 地照料一个孩子，这会给你的生活带来无穷的 ，使你变得年轻，头脑变得 ，心情变得快乐，身体更加健康.

There are four options provided, respectively 准许、适应、兴趣、灵敏；批准、合适、快乐、灵巧；允许、适当、兴趣、灵活and  同意、适合、爱好、机灵. According to the possible answers, foreigners who learn Chinese in China can guess the general meaning. It says aged people can take care of children if possible because it will bring pleasure to them and become flexible. When learning in free Chinese lesson, you should know we often use允许to express if the conditions are allowed. The best word for replacing proper is 适当 and pleasure means 乐趣. When we intend to say flexible, we usually choose 灵活.