we know that
An polynomial is an expression of more than two algebraic terms, especially the sum of several terms that contain different powers of the same variable
option-A:

since, there are two variables
so, this can not be polynomial
option-B:

Since, there is a only one variable
so, this is a polynomial
option-C:
Since, there is sqrt
and in polynomial exponent can not be fraction
so, this is not polynomial
option-D:

since, there is only one variable
so, this is polynomial