The correct answer is C. 2 bogie or its equivalent.
A bogie is a frame or platform on which railway wheels are mounted. It is a fundamental component of railway vehicles, and is used to support the weight of the vehicle and its load, and to provide stability and traction.
The number of bogies that can be attached to a goods train in the rear of a BV (break van) is determined by the weight of the train and the type of bogies used. In general, two bogies or its equivalent are required to provide adequate stability and traction.
Option A is incorrect because it specifies a maximum of two bogies. This may not be sufficient for trains with a heavy load or that are operating in difficult conditions.
Option B is incorrect because it specifies a minimum of one bogie. This may not be sufficient to provide adequate stability and traction for some trains.
Option D is incorrect because it does not specify a specific number of bogies. This is not a valid answer to the question.