The declaration section holds

The correct answer is: C. data members, function prototypes, and the functions themselves.

The declaration section of a class holds the data members and function prototypes of the class. The data members are the variables that belong to the class, and the function prototypes are the declarations of the functions that belong to the class. The functions themselves are defined in the implementation section of the class.

Option A is incorrect because it only includes data members. Option B is incorrect because it only includes data members and function prototypes. Option D is incorrect because it includes none of the above.