It is our duty to defend our country.
保卫国家是我们的义务 不可数
Customs duties are paid on imported goods.
对进口货物征收关税。 可数
One of my duties is to file the letters.
我的职责之一是将信件归档。 可数
I decided to make one more effort.
我决定再作一次努力。 不可数
His efforts had no smallest chance of success.
他的努力毫无成功的希望。 可数
His recent novel is a fine literary effort.
他新近的小说是一本文学佳作。 不可数
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