The correct option is C Could
The context indicates a request for borrowing.
Thus, "could" in option B is correct. The modal 'could' is used to make a suggestion or a request. This matches the context of the given sentence.
"Can't" in option B is incorrect as negative modal is not used to make a request.
"Manage to" is incorrect as it implies something that has been achieved despite difficulties.
"Couldn't" is the negative contraction. Negatives are not used to make request.
Thus, option B is the correct answer.