Answer:

Linear Polynomial:
A linear polynomial is a polynomial of degree 1, which means it has one term raised to the power of 1. The general form of a linear polynomial is ax + b, where a and b are constants and x is the variable.

Given Polynomial:
The given polynomial is 1 + 3x. This polynomial has only one term with the variable x raised to the power of 1. Therefore, it is a linear polynomial.

Explanation:
To determine the degree of a polynomial, we look at the highest power of the variable. In this case, the highest power of x is 1, so the degree of the polynomial is 1.

Option Analysis:
a) Quadratic: A quadratic polynomial is a polynomial of degree 2, which means it has a term raised to the power of 2. Since the given polynomial does not have any term with x raised to the power of 2, it is not a quadratic polynomial.
b) Cubic: A cubic polynomial is a polynomial of degree 3, which means it has a term raised to the power of 3. Since the given polynomial does not have any term with x raised to the power of 3, it is not a cubic polynomial.
c) Linear: As explained earlier, a linear polynomial is a polynomial of degree 1, which means it has a term raised to the power of 1. The given polynomial has only one term with x raised to the power of 1, making it a linear polynomial.
d) None of the above: This option is incorrect because the given polynomial is a linear polynomial.

Therefore, the correct answer is option 'C' - Linear.