His knowledge about the subject is very profound.
他在这方面的知识非常渊博。

2. afflict v. 使痛苦,使苦恼,折磨

Famine and war still afflict mankind.
饥荒与战争依旧给人类带来痛苦。

3. pledge v. 保证给予;许诺;发誓

They love freedom and pledge their lives for their love.
他们热爱自由，愿为他们的所爱抛头颅洒热血。

4. unassailable a. 不容置疑的

It signified to him the unassailable power of the companies.
这向他表明了公司那不容置疑的威力。

5. strive v. 努力,苦干,奋斗

I strive for the best, and I do the possible.
我尽力而为争取最佳。