in a day的用法和樣例：
例句
- Can I go there and back in a day?
我一天內能打來回嗎? - Rome was not build in a day.
[諺]羅馬非朝夕建成。 - He used to be able to cycle50 miles in a day, but he's past it now, I'm afraid.
他過去一天能騎50英里，不過現在恐怕不行了。 - 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。 - Rome was not built in a day.
偉業非一日之功。
