The professor is never at a nonplus, and never perplexed by a problem.

那位教授从来不会感到困惑，也不会被任何问题所难。

The difficult problem present by him entangle the conferee.

所提出的问题与会人士感到困惑。

He was still more perplexed, for this inconsequent smile made nothing clear.

然更加感到困惑，因为这突如其来的，感到莫名其妙。