1-C. However, Mr. Matsumoto is such an obstinate person that he will not listen to them and continues to spend a lot of time making up jokes for his classes.However, Mr. Matsumoto is such an obstinate person that he will not listen to them and continues to spend a lot of time making up jokes for his classes.
2-C. In this situation, "an obstinate person" means a person who is unwilling to change his mind.In this situation, "an obstinate person" means a person who is unwilling to change his mind.