You have that:
1. By definition, a binomial is a polynomial formed by two terms.
2. A quintic binomial is a binomial of degree 5. This means that its highest exponent is 5.
3. Keeping this on mind, you must identify which binomial has degree 5.
4. As you can see, the expression 3x^5+2 is a binomial, because it has two terms and the highest degree is 5.
5. Thefore, the answer is: 3x^5+2