dai的用法和樣例：
例句
- After being taken back 200 years, we were suddenly returned to the present day.
我們剛才還處在200年前的歷史場景之中，一下子又回到了現在。 - She smokes 20 (cigarettes) a day.
她一天抽20支(香煙). - In a day, a doctor may write (out) 30 prescriptions for patients.
一個醫生一天可能要給病人開出30張處方。 - He makes nothing of walking 20 miles in a day.
一天走20英里，他不以為是難事。
