be sure of
确信
例句与用法：
Can I be sure of a profit if I invest?
我要是投资，肯定能获利吗?
Book early if you want to be sure of a seat.
要想十拿九稳有个座位，那就早订座。
I left a message so as to be sure of contacting her.
我留下了张条子以便与她取得联系。
He likes to be sure of his bodily comforts.
他注重身体上的舒适。