A polynomial is made up of terms.
A term is a single number or a number multiplied by one or more variables.
A polynomial can be a single term or a sum of terms.
In a polynomial, there is no division by variables.
Polynomials: Options 1, 2, 4, 5, 6
Not a Polynomial: Option 3
If the terms have at most a single variable, then if the highest exponent on a variable is a 2, then the polynomial is quadratic. If there is only a single variable with no exponent, then it is linear.
Option 1: quadratic
Option 2: linear
Option 3: not a polynomial
Option 4: linear
Option 5: quadratic
Option 6: linear