Which statement is a proposition?
a. she set sail on tuesday.
b. why are you late?
c. good afternoon!
d. what happened to my sandwich?

The answer is A: She set sail on Tuesday.  This statement is a proposition. The statements in B and D are interrogative sentences. The statement in C is a greeting.  A proposition is a statement or a suggestion offered for consideration.  In logic, it's an expression that may be true or false, it can be affirmed or denied. There is the purpose of determining the validity of a claim.

it is the background information on the characters and setting explained at the beginning of the story. the exposition will often have information about events that happened before the story began. the exposition is often the very first part of the plot.