Which of the following is true about 9?
A. It is an integer but not a rational number
B. It is both an integer and a whole number
C. It is a whole number but not an integer
D. It is an integer but not a whole number
B. It is both an integer and a whole number
The correct answer is B. It is both an integer and a whole number.
An integer is defined as a whole number, either positive, negative, or zero. Since 9 is a positive whole number, it is considered an integer and a whole number.