here is a run down of what each word means:
Binomial: there are two terms. (for example, 7x + 8y)
Trinomial: there are three terms. (for example, 13x² + 8y³ + z)
Monomial: There is only one term. (for example, 17x³)
Multinomial: Many terms, specifically more than 3 (4 or more terms).
The question given shows:
-9n^6p^6y^5 + 2x³ - 8g^4r².
-9n^6p^6y^5 is one term.
+2x³ is another term.
-8g^4r² is the last term.
Therefore, there are 3 terms.
3 terms = trinomial, ∴ you're answer is trinomial, or B
hope this helps
