Answer with explanation:
The Expression which is equal to ,

in which 97 is Prime Number, and x is a Variable.
So, for further Simplification, x must be a Composite Number, having two Identical Factor.
For, x=5,
, can not further Simplified.
For, x=10,
, also can not further Simplified.
For, x=15,
, can not be further Simplified.
But for, x=20

The Expression can be further Simplified.
Option D: 20