Answer:
The substitution that can be made in order to convert the equation into quadratic equation is:

Hence, option: C is correct.
Explanation:
We are asked to find the substitution that can be made in order to convert the given degree six polynomial equation into a quadratic equation i.e. degree 2.
We are given a polynomial equation as:

We know that a quadratic equation is written in the form:

where a,b and c are real numbers.
Hence here if we substitute:

We get:

Hence, the equation get converted into:

Hence, the substitution is:
