C. all the other sentences have direct characterization in them. c doesn’t seem to have that. you would have to infer those traits.
THe answer is A. Themselves. A reflexive pronoun indicates that the person who is realizing the action of the verb is also the recipient of the action.
My answer would be leadership or management. This is because as a leader, you manage other people, you supervise other people, you hopefully motivate other people and as a leader you need a good strategy.
The art of getting things done through people.
Leadership.