Because he is not a fitter in factory A but a lathe worker in factory B, Wang is not in factory A or factory B, but in factory C;
Because Zhang is not in factory A, but in factory B, he is a lathe worker, so Zhang is in factory B;
Zhang is a lathe worker in factory B, Wang is a fitter in factory C and Li is an electrician in factory A..
So the answer is: √.