How many of the above are considered as alternative powertrain vehicles?

Explanation : 

Alternative powertrain vehicles

Alternative powertrain vehicles refer to vehicles that use propulsion systems other than conventional internal combustion engines powered solely by gasoline or diesel. The given types of vehicles are:

I. Full battery electric vehicles (BEVs): These vehicles run entirely on electricity stored in batteries and do not use conventional fuels.

II. Hydrogen fuel cell vehicles (FCVs): These vehicles use hydrogen gas to generate electricity through fuel cells, powering an electric motor. They emit only water vapor as exhaust.

III. Fuel cell electric hybrid vehicles: These vehicles combine hydrogen fuel cell technology with battery-electric technology, using both fuel cells and batteries to power the vehicle.

All three types mentioned above represent alternative powertrain technologies, as they deviate from traditional internal combustion engine vehicles. Hence, the correct answer is option (c) All the three.