useful to的用法和樣例：
例句
- It's always useful to have something to fall back on.
有點依靠的東西總是有用的。 - It's more useful to learn modern languages, such as English and German, than Latin.
學習英語和德語等現代語言比學習拉丁語更為有用。 - He is useful to his father.
他對于他的父親很有用。 - This reference book is very useful to our study.
這本參考書對我們的研究很有用。 - John always tries to cultivate people who are useful to him.
約翰經常設法和對他有用的人結交。
