Answer:
Intrinsically motivated
Explanation:
Since Kevin was not enrolled in a school nor have a job that his mathematical reasoning would help him either pass a test or solve a problem at work, the reason for his motivation is driven by internal rewards. Hence Intrinsic motivation can be defined as a behavior, not driven by any external motivation, but by internal rewards. The motivation for Kevin wanting to learn mathematics on his own comes from within and is naturally satisfying to Kevin.
D. Trachea, is the answer.
