Please add your modes of narration
I would assume C. Management
Since nothing is underlined i presume that the underlined pronoun is them. It is in the dative case because them is an object and answers the question to whom was something done. Them refers to the trainer's team.
Answer:
Dr Hewitt is able to break the piece of wood in his demonstration given that he had knowledge about the concept of momentum, which is esentially the product of the mass and speed of an object.
Aplying this idea, he used the correct momentum of his hand over a short period of time and that is how he was able to break the piece of wood.