The OA is E, I think it should be C


1) aba=a so a^2b-a=0
a(ab-1) = 0

so either a=0 or ab=1

2)

aba=b so b^2a-b=0
b(ab-1) = 0

so either b=0 or ab=1

combining 1 and 2, ab=1


Please help