乃是的用法和樣例：
例句
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因此，對一個(gè)從事社會(huì )活動(dòng)的人來(lái)講，培養一種嗜好和新的情趣方式，乃是至關(guān)重要的對策。
The cultivation of a hobby and new forms of interest is therefore a policy of first importance to a public man. -
將在適當的時(shí)候加以說(shuō)明的，乃是這一數字的來(lái)源。
It is how this number is known that will be described in due course. -
我遇到她乃是上上個(gè)禮拜。
It was the week before last that I met her.
