certain的副詞：certainly；
certainly
adv. 當(dāng)然；行（用于回答）；必定
例句：
Moby certainly has a fine ear for a tune.
莫比對(duì)音調(diào)的分辨能力一定很強(qiáng)。
He certainly was not politically inactive.
他在政治上當(dāng)然不是無所作為。