Hello!
An irrational number cannot be written as a fraction. Let's look at our options.
In D, the exponent and square root cancel each other out. This leaves us with ten, which is a rational and whole number.
For B, and repeating decimal can be written as a fraction using a specific formula. Therefore B is also rational.
For A, the square root of 196 is 14, which is a whole number and is therefore rational.
For C, the square root of 8 is 2.8284....... and continues on in no specified order. Therefore it cannot be converted into a fraction. Therefore, C)√8 is irrational.
I hope this helps!