Which of the following must describe a irrational number? A. a number with a repeating or terminating decimal expansion B. a number with a nonterminating decimal expansion C. a decimal with a nonrepeating decimal expansion D. a number with a nonrepeating and nonterminating decimal expansion

D.

Step-by-step explanation:

A irrational number can be defined as those numbers which are real but can NOT be expressed in simple fractions. The term 'irrational' means 'a number which can not be expressed in ratio of two integers', 'no ratio.'

When a irrational number is expressed in decimal, the numbers keep on expanding without repeating andd without terminating, which means it keeps on expanding infinitely.

For example, π (pi) is an irrational number. When it is expressed in decimals it keeps on expanding non-repeatedly and unendingly.

Another example of an irrational number is √2.

Thus the correct statement that defines irrational number is option D.