Answer:
- An integer is not negative if and only if it is not less than zero.
Explanation:
Observing each statement individually:
- An integer is negative if and only if it is not less than zero
A number that is NOT less than 0 is greater than zero. Negative numbers are less than 0, so this is clearly incorrect.
- An integer is not negative if and only if it is less than zero.
A number that is NOT negative is positive. Positive integers are integers greater than zero, so this is also incorrect.
- An integer is not negative if and only if it is not less than zero.
A number that is NOT negative is positive. A number that is NOT less than zero is greater than zero, or positive. This statement is correct.
- An integer is less than zero if and only if it is not negative.
A number that is less than zero is negative, and this statement claims that a number less is only less than zero if it is NOT negative. This is incorrect.