to sb.'s certain knowledge

例句：

1. 1. I have toknow the answer before I can help you.
   在帮助你们之前，我必须知道答案。
2. 2. She had to rely on her owncertain knowledge to solve the problem.
   她不得不依靠自己的确切知识来解决这个问题。
3. 3. The scientisthad to consult his certain knowledge of thesubject to make an accurate prediction.
   科学家不得不参考他对这一主题的确切知识来进行准确的预测。