Step-by-step Solution:

The idiom spill the beans means to accidentally or deliberately reveal a secret or confidential information. Let us analyze the options: (a) To be untidy - This is incorrect and unrelated to the idiom.\[\] (b) To be very talkative - This is incorrect as it does not necessarily imply revealing secrets.\[\] (c) To reveal something that is supposed to be kept secret - This is the correct meaning of the idiom.\[\] (d) To leave a place quickly - This is incorrect as it does not relate to the meaning of the idiom.\[\] \[\] Correct Answer: (c)