An integer data type is used to represent whole numbers without any fractional or decimal component. In the given options:

A. The number of students in a section is a countable quantity that does not require a fractional part, making it suitable for an integer data type.

B. The cost of a dinner including tax and tip would typically involve a decimal to account for cents, thus requiring a floating-point data type.

C. The weights of patients are usually measured with precision and can have decimal values, necessitating a floating-point data type.

D. An approximation of the number pi to five decimal places is a decimal value and would require a floating-point data type.