Answer:
Payment before publication of a book.
Explanation:
From the given passage, it is evident that the speaker is talking about how he was relieved and happy to have finally got his book accepted. Moreover, he also revealed that he had been given an advanced payment for that same manuscript.
In this regard, the word "advance" refers to the advanced payment given to him before the publication of the book. An advance is something that is given before the actual execution of the deal or agreement between the parties, in this case, the publication of the book.
Thus, the correct answer is the second option.
