What is the "big book" Candide playfully refers to when asking Martin if he believes "the earth was originally all ocean, as they assure us in the big book belonging to the ship's captain"?

The "big book" that Candide was playfully referring to is the Bible.

Explanation:

The novel "Candide" by Voltaire revolves around the optimistic character of Candide. Though at times seemingly silly, he is just the way he is, always optimistic about things.

In Chapter 21, we see Candide and Martin returning to the coast of France. It was then that Candide asked Martin whether he has been to Paris which prompted a reply from the other man that it is a land of disgusting, manner-less people. When asked why he thinks the earth is created by God, he said "To make us mad". It is in this scene that the differing philosophies of the two is evident, Martin believing in the permanent bad nature of men whereas Candide believes that man is capable of change in the future, even if not drastically. The scene shows Martin's faith and belief in God being questioned by Candide.

answer; i do believe its (b) 12.5 years of age;