The Sony PCM-M10 would work fine. The issue that would arise with any recorder in this setting is the proximity of sounds nearby the unit. The mics, regardless of their quality, are going to pickup what sounds are closest to them (i.e. typing, coughing, ruffling of papers, etc.) and they will stand out during playback. Perhaps you could ask your instructor if you could place the recorder on the podium/desk up front. This would make the instructor more prominent in playback, but questions coming from the audience might not be as discernible.