Option a: 
Option b: 
Option c: 
Explanation:
The highest degree of a polynomial is the largest exponent of that variable.
Now, we shall determine the polynomial with degree 3.
Option a: 
From the expression
, the highest degree of the polynomial is 3.
Hence,
is a polynomial with a degree of 3.
Hence, Option a is the correct answer.
Option b: 
From the expression
, the highest degree of the polynomial is 3.
Hence,
is a polynomial with a degree of 3.
Hence, Option b is the correct answer.
Option c: 
From the expression
, the highest degree of the polynomial is 3.
Hence,
is a polynomial with a degree of 3.
Hence, Option c is the correct answer.
Option d: 
From the expression
, the highest degree of the polynomial is 1.
Hence,
is a polynomial with degree 1.
Hence, Option d is not the correct answer.