The degree of a polynomial is the highest power of the variable $x$ present in the polynomial expression. The given polynomial is:

$x^5 + 1 - 3x^4 + 3x^9 - 2x$

Now, let's identify the degrees of each term:

• $x^5$ has degree 5.
• $1$ (a constant) has degree 0.
• $-3x^4$ has degree 4.
• $3x^9$ has degree 9.
• $-2x$ has degree 1.

The highest degree among these terms is 9, which comes from $3x^9$.

Therefore, the degree of the polynomial is 9. The correct answer is D.

Would you like any further explanation?

Here are 5 related questions to practice:

1. What is the degree of the polynomial $2x^7 - x^3 + 4$?
2. How does the degree of a polynomial affect its graph?
3. What is the degree of the sum of $x^4 + 3x^2$ and $x^5 - 2x + 1$?
4. Can a polynomial have a degree of 0? What would that look like?
5. What is the degree of the product of $x^2$ and $3x^5$?

Tip: The degree of a polynomial is key in determining the end behavior of its graph.