Answer:
It's A.
I'll give some examples if you are confused.
Monomial would be- 3xy^2
Binomial would be- 5x - 1
Trinomal would be 3x + 5y^2 - 3
I highlighted the numbers and letter too. The monomial is highlighted representing one thing. Binomial has 2 highlighted things and Trio has 3 highlighted things. Hopefully you understand.
Have a great day.