Final answer:
A third-degree polynomial is written in standard form by arranging the terms in descending order of exponents: x³, x², x, constant term.
Step-by-step explanation:
A third-degree polynomial is a polynomial of degree 3, meaning the highest power of x is 3. To write a polynomial in standard form, the terms should be arranged in descending order of exponents, starting with the term with the highest degree.
Among the given options, the polynomial (a) (3x³ + 6x² + 5x - 9) is in standard form because the terms are arranged in descending order of exponents: x³, x², x, constant term.