A rational number has has a terminating decimal expansion or a decimal expansion of non-terminating repeating digits. Here, the decimal expansion is terminating, so it is a rational number.
A rational number is any number that can be expressed as a fraction. So for example, since cant be expressed as a fraction, it isn't rational. A number like 1.25 on the other hand IS rational as it can be expressed as or .
Option C can be expressed as , so it must be rational.
- Note that if a number has a finite amount of digits after the decimal (ie it doesn't go on forever like option B), it can be represented as a fraction and thus is rational.