I voted Pedal Assist (which I assume is electric). Gas is ok but around here it would limit the vehicle to roads only. Local greenways do not permit gas powered bikes as they are considered Mopeds under State Law. This designation also means motorcycle type helmet, registration, and insurance. An engine 50cc or above would make it a full-fledged motor vehicle. Engines are noisy and smelly too. I'm not sure I would want to be enclosed in the same small place as one.
Also, full electric without pedal assist may meet the NC definition of a Moped, though I'm not sure. Even if not, many greenways/trails around the country prohibit e-bikes with throttles.
No issue if one will only ride on streets. Although I do see a lot of recumbent trikes (some with E-motors) on greenways, I have not yet seen one shelled out like a velomobile.