On Saturday, the bookstore sold x books. On Sunday, the bookstore sold 3 more books than on Saturday. The expression 2x + 3 represents the total number of books sold over the weekend.
What does the "2" represent in the expression 2x + 3?

A.the number of books sold on Saturday
B.how much more books were sold on Saturday
C.the total number of books sold
D.the number of days