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

那位教授从来不感到，也不被任何问题所难倒。

The difficult problem present by him entangle the conferee.

他所提出的问题使与感到。

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

他然更加感到，为这突如其来的一笑，使他感到莫名其妙。