1. ~ sb. that + clause
eg.
I assure you that there is no danger. 我向妳保證沒有危險。
We tried to ~ the old lady that flying was safe. 我們盡力說服那位老婦人讓她相信飛行是安全的。
2.~ sb. of sth.
eg.
He assured me of his readiness to help. 他使我相信他樂意幫忙。
3.~ sth
eg.
Nothing can assure permanent happiness. 沒有東西能保證永久的幸福。
以上例句來自《牛津現代高級英漢雙解詞典》。
希望對妳有所幫助！