Answer:
B. who can immediately take over the family business
Explanation:
Option A is wrong because opportunity cost is not related to intelligence.
Option C is not correct because a high school graduate and a college attending student can access to student loans.
The family's wealth can not be a factor in terms of opportunity cost of attending college or a high school graduate. Therefore, option D is incorrect.
Option B is correct as a college attending student cannot take over the family business. So, it is his opportunity cost. On the other hand, a high school graduate can take over the business.