The correct option is C some
The options given are pronouns that refer to an unspecified quantity or number. The given sentence tells us that the speaker was lent an 'amount of money' out of which an unspecified amount is still left. When we place 'any' in the sentence, the sentence sounds incomplete, because 'any' is used in negative sentences, and would be phrased this way 'I don't have any money...', but the sentence calls for a positive pronoun because there is an amount of money left. Similarly, 'much' when referring to money, is used in the negative sense 'I don't have much money', hence options A and B are incorrect. 'Less' means 'lower in quantity', it has a negative connotation and the sentence does not connote a negative meaning, 'less' when referring to money, is not followed by 'of the', hence option C is incorrect. 'Some' refers to an unspecified quantity in the positive sense, and the sentence sounds complete when it's placed, hence option D is correct.