Heat supplied to a system (q) = MC delta T. So if it is isothermal then heat supplied will be 0? But how is this possible?

For isothermal change dT = 0 and dE =0 but there is change in enthalpy which can be calculated using the formula
Q = dE +d ( PV)
   = 0 + d(PV)
Thus the PV work decides about the enthalpy change. Not by the above formula its decided