D) 5
Reason: It's the largest exponent
When a polynomial is written in standard form like this, the term with the largest exponent is written first, then the next largest and so on. Â So in cases like this, we simply need to look at the left-most term; however, this may not always be the case as your teacher could easily mix up the terms to make sure you're paying attention.
This is considered a quintic polynomial due to the degree of 5.