Which one of the following is not true?
A. When x is not a perfect square, is an irrational number

B. The index form of

C. The radical form of

D. Every real number is an irrational number

As in

Option A

As we know an irrational number are those number which cannot be represented in simple fraction

Hence they are not perfect square

For example 3 is not a perfect square

also is irrational number

hence A is true

option B

index form of number means power form

as

hence B is true

Option C

Radical form means surd form

Hence C is also true

Option D

It is not true that every real number is a rational number

For example 2 is real number but not irrational number

Hence D is not true

Hence D is the right answer