Answer:
√70
Explanation:
An irrational number is a number that cannot be expressed as a simple fraction and has an infinite, non-repeating decimal representation. Examples of irrational numbers include √2, π, and e.
Of the numbers you listed, √70 is an irrational number. The other numbers are not irrational because they can be expressed as simple fractions: √16 = 4, √1 = 1, and √81 = 9.