Which set of numbers is always irrational?

A. Repeating decimals
B. Positive decimals
C. Terminating decimals
D. Non-terminating, non repeating decimals

D. Non-terminating, non-repeating decimals

The correct answer is D. Non-terminating, non-repeating decimals. These numbers cannot be expressed as fractions and have an infinite number of non-repeating digits after the decimal point, making them irrational numbers.