Which expressions are polynomials? select each correct answer. see photo.

Polynomial: is a mathematical expression of one or more algebraic terms each of which consists of a constant multiplied by one or more variables raised to a non-negative integral power 
With this definition we can eliminate the first one and second one. 
The third one cannot be right because it does not have a constant being multiplied by a variable and so on. 
I think it is the last one since it is the only one that has a constant multiplied by a variable raised to an integral power. 
D is correct. 

For the first question the answer is a, for the second c, for the third d, for the 4th b, for the 5th a