Answer
Александр
The correct sentence:
John passed his exams successfully, so he can afford to go to any university.
The only choice “John passed his exams successfully, so he can afford to go to any university” is correct and logical: he passed his exams successfully, (so) he can afford.
Choices “John passed his exams successfully, or he can afford to go to any university”, “John passed his exams successfully, but he can afford to go to any university” and “John passed his exams successfully, yet he can afford to go to any university” make no sense because there is a wrong causal relationship.