短語動詞是一個整體，不可丟掉后面的介詞或副詞。例如：
My sister will be taken care of by Grandma. 我妹妹由奶奶照顧。
Such a thing has never been heard of before. 這樣的事聞所未聞。
My sister will be taken care of by Grandma. 我妹妹由奶奶照顧。
Such a thing has never been heard of before. 這樣的事聞所未聞。