Which of the following is an example of a rational number?

A rational number is defined as a number that can be expressed as the quotient of two integers, where the denominator is not zero. In this context, 4.5 is a rational number because it can be written as a fraction: 4.5 = 45/10, which simplifies to 9/2.

This confirms that 4.5 meets the criteria for rationality since both 45 and 10 are integers, and the denominator (10) is not zero. Therefore, it qualifies as a rational number.

In contrast, other options such as π (pi), √2, and e are known to be irrational numbers. They cannot be expressed as fractions of two integers, and their decimal expansions are non-repeating and non-terminating. This characteristic is what sets irrational numbers apart from rational numbers.