Which of the following is true about −9?
1) It is both an integer and a whole number.
2) It is an integer but not a whole number.
3) It is an integer but not a rational number.
4) It is a whole number but not an integer.
1) It is both an integer and a whole number.
The correct option is:
1) It is both an integer and a whole number.
An integer is any positive or negative whole number, including zero. −9 falls into this category as it is a negative whole number. Additionally, a whole number is any positive or non-negative integer, so −9 is also considered a whole number.