For an electric airplane are propellers the only option for propulsion?
Propellers in some form are really the only option. It is currently the only efficient way to generate thrust with air as a medium. Even jet engines are in some sense just a very elaborate system of propellers.
The reason for the turbine is to create an environment to efficiently burn fuel (suck, squeeze, bang, blow) to generate as much thrust as possible. Hence, in an electric aircraft this is irrelevant. You might be interested in the Airbus E-Fan, which uses ducted propellers increase efficiency. However, it is still 'just' a propeller with an electric motor in the middle.