Answer:
A. 9x² - 7
Explanation:
» Concepts
A monomial is an expression that consists of only one mathematical term.
A binomial is an expression that consists of only two mathematical terms joined by an addition (+) or subtraction (-) sign.
A polynomial is an expression that consists of three or more mathematical terms joined by an addition (+) or subtraction (-) sign.
» Solution
Given these definition, we can surely determine that A. 9x² - 7 is the correct answer because it's the only answer choice with only two terms. B is a polynomial, and C and D are monomials.