We have three finitely presented groups
A is generated by two generators a and b and one relation
B is generated by three generators a, b, c and three relations , .
C is generated by four generators a, b, c, d and four relations , , and .
Test your intuition: which of the groups A, B or C is trivial
Please do not answer this poll if you already knew the answer
This poll is to learn how many people already knew the answer before. Please please answer.
As always comments are welcome!
Update: I did not know the answer (and I feel now better about it).