Which of the following is not an integer? (a) 0 (b) -1 (c) -1.5 (d) 1

To determine which of the given options is not an integer, let us analyze the choices:

What is an integer? Integers are whole numbers that can be positive, negative, or zero. They do not have fractional or decimal parts. Examples include -3, -2, -1, 0, 1, 2, 3, etc.

Analysis of each option:

(a) 0: Zero is an integer because it is a whole number without a fractional or decimal part.
(b) -1: Negative one is also an integer because it is a whole number without any fractional or decimal part.
(c) -1.5: Negative one point five is not an integer because it has a fractional part (0.5). It is a rational number but not an integer.
(d) 1: Positive one is an integer because it is a whole number without any fractional or decimal part.
Conclusion: The option that is not an integer is (c) -1.5.