The correct answer is B. 8.
A 4-8-2 locomotive is a steam locomotive with four leading wheels, eight driving wheels, and two trailing wheels. The driving wheels are the wheels that actually power the locomotive. The leading and trailing wheels are used for steering and balance.
The number of driving wheels in a locomotive is important because it determines how much power the locomotive can generate. The more driving wheels, the more power the locomotive can generate. This is why 4-8-2 locomotives are often used for pulling heavy trains.
The other options are incorrect because they do not represent the number of driving wheels in a 4-8-2 locomotive. Option A, 4, is the number of leading wheels. Option C, 12, is the total number of wheels. Option D, 14, is the number of wheels if the trailing wheels are included.