Students use the difference of how to pronounce the answers help to choose. He used to observe from the mouth of the trainer and feel the difference while vote manually.
Students use a different method of voting to help select the right answer. He used observations from the mouth of the trainer and feel the difference in their vote.
Students use the difference of the way to pronounce help in choosing the answer. He used to observe from the mouth of the trainer and feel the difference as pronounced by themselves.