The set S={1,4,9,16,25,36} in the descriptive form is
A.{Squares of naturals numbers}
B.{x|x is a square of a natural number}
C.The set of squares of first six natural numbers
D.$x|x = {x^2},n \in N{\text{ and }}n \leqslant 6$

Hint: Descriptive form is nothing other than saying about the elements of the set in words. The description must allow a concise determination of which elements belong to the set and which elements do not.

Complete step-by-step answer:
Step 1:
Here our given set is $S = \left\{ {1,4,9,16,25,\left. {36} \right\}} \right.$.
It is clearly understood that each and every element of the set is a perfect square.
(i.e.)
$\begin{gathered}
  {1^2} = 1 \\
  {2^2} = 4 \\
  {3^2} = 9 \\
  {4^2} = 16 \\
  {5^2} = 25 \\
  {6^2} = 36 \\
\end{gathered} $
Step 2:
So it is clear that it is a set of perfect squares .
But ,we can see that we have only 6 elements,that is we have only the squares of the first six natural numbers
Step 3:
In descriptive form, we need to describe the elements in words ,just in a simple sentence.There is no need to use set braces while writing in descriptive form and everything should be said in words and not using symbols.
Step 4:
Therefore ,the descriptive form of the above set is that it is the set of squares of the first six natural numbers.
The correct option is C

Note: Descriptive form is one way to specify a set by giving verbal description of its elements.
Descriptive form is also known as statement form
The other two types of representing a set are set builder form and roster form.