Yes, it was just a misprint. But what about the rest (a, b, d)? What is so unnatural about them?
The alternatives I've given were meant to ilustrate why there were better alternatives. They probably failed because I'm not sure why they don't sound unnatural. I only know they do.
I'll give it another shot.
a) Jim is hesitant to apply to university, thinking his family will not be able to afford the tuition.
Jim has not applied yet. Therefore "would not be" is more appropriate than "will not be".
"Will not be " works for "Jim is sorry he applied, thinking that his family will not be able to pay if he is accepted." Note that "if he is accepted" makes a big difference"
"If he does apply, his family will not be able to pay"; "If he did apply, his family would not be able to pay."
b) Jim will be hesitant to apply to university, thinking his family cannot afford the tuition. (his family doesn't have enough money) will not be able :up:
d) Jim has been hesitant to apply to university, thinking his family will not be able to (cannot) afford the tuition. (he is still hesitating because he doesn't believe his family will have enough money to fund his tuition after his classes begin)
The objection is simlar to a). It would be natural to say, "Jim has been sorry ever since he applied to university, knowing that his family will not be able to pay if he is accepted".
Maybe changing "thinking" to "knowing" even makes a difference.