Answer:
B. by identifying the parts of the rocket is the correct answer.
Step-by-step explanation:
To indicate the correct answer, let's use the discarding method.
Letter A is incorrect because the name of the inventor of the rocket is not relevant to indicate the necessary parts for a real launch.
Letter C is incorrect because it could go in the wrong direction, meaning that the boy could me more skeptical if the rocket were compared to a toy, even though some parts were similar.
Letter D is an important part to let the boy know how the rocket was launched, but this could be also shown with a toy or any other item, as long as it has a similar shape.
Finally, letter B is correct because a model is a representation (3D) of someone or something, and it usually shows in detail (as much as possible) the parts of a machine, like in the question. By this, the boy would understand why the model is not a toy.