1. But we were afraid that the strength of the current would prevent its landing anywhere before it became exhausted.
    但我们担心，洪水力量将使它上岸之前就筋疲力尽了。

2. One of the best answers he's ever received came from an 86-year-old man who learned the ancient Chinese exercise form of tai chi as part of Wolf's study of how exercise can help seniors prevent falls.
    他得到的最佳答案之一来自一位86岁的老人。沃尔夫研究的是运动如何帮助老年人防止摔跤，而作为该研究的一部分，这位老人修习一种古老的中国健身法——太极。

3. In particular, he studied how to prevent a wounded man from bleeding too much, and also he studied the nerve system in the bodies of animals and humans.
    特别是，他研究了怎样防止伤员流血过多。同时还研究了动物和人体的神经系统。

4. I should transport the gun from my residence to my vehicle, but I don't. What the gun is capable of, what it is intended for, still frightens me more than what it may prevent.
    如果我带着枪的时候遭到了袭击，那我就必须用它来杀人，而不仅仅是伤人。