Use of GFCI

You should check the local building code to be sure. There are some good reasons why most plugs have three prongs nowadays. If your wiring is old, before the change to three prong outlets, there is a chance that the insulation has lost its flexibility and can part to allow a wire to touch the metal box that holds the outlet. That is called "creep". That happened in my house. Fortunately it only tripped the breaker, so I called an electrician to find the problem and fix it.

An electric current produces a magnetic field, and that can be used to operate a switch. If both wires are together, the field of one wire cancels the field of the other. If there is any fault, some current will go out one wire but not come back on the other, so the field is not canceled and that trips a switch and breaks the circuit. We call that GFCI: Ground Fault Circuit Interrupter.