Please help me with this question.

What particle has exactly one quantums unit of charge?

1 answer

an electron has one unit of charge.

Your use of quantum is unusual, in the standard model of matter, their is a number of types of charge, and the particle that carries most is the guage boson. I doubt if your teacher meant this meaning in the use of quantum, however, it is the answer to what was asked.

http://en.wikipedia.org/wiki/Charge_(physics)