The young man appears to be quite headstrong.

The correct answer is B. obstinate.

Headstrong means determined to do something in spite of opposition or difficulty. It is often used to describe someone who

Thick-headed means stupid or slow-witted.

Robust means strong and healthy.

Witty means clever and amusing in speech or writing.

In the context of the question, the young man appears to be determined to do something, even if it is difficult or others try to stop him. This suggests that he is obstinate.