Which one of the following is not a rational number? A. √2 B. 0 C. √4 D. √16

To solve the given question, we need to identify which number is not a rational number. A rational number is any number that can be expressed as the quotient or fraction of two integers, where the denominator is not zero.

Let's analyze each option:

A. √2:
The square root of 2 is an irrational number. It cannot be expressed as a fraction of two integers because it has a non-terminating, non-repeating decimal expansion. Hence, √2 is not a rational number.

B. 0:
Zero is a rational number because it can be expressed as the fraction 0/1. Any integer, including 0, is a rational number.

C. √4:
The square root of 4 is 2, which is a whole number and thus a rational number. It can be expressed as the fraction 2/1.

D. √16:
The square root of 16 is 4, which is a whole number and thus a rational number. It can be expressed as the fraction 4/1.

Conclusion:
The correct answer is A. √2, as it is the only option that is not a rational number.