"게는 개가 아닙니다."
Translation:A crab is not a dog.
IMHO, it is possible to distinguish the sound difference in this exercise in particular.
ㅔ seems to be a "close/low/downward" sound. I would represent it like this "ê" in my native language. On the other hand, ㅐ seems to be a more "open/high/upward" sound. It would be something like this "é" in Portuguese.
Although, by my limited experience, I don't see them being used consistently in Korean.