Answer:
A), B), E), F)
Explanation:
Like terms are terms with the same variable part. That means the same variables and exponents. Also, two terms with no variables are like terms.
A) 9x^2 and 5x are not like terms
B) a^2 and 2a are not like terms
E) 2x and 2y are not like terms
F) 3x and 3xy are not like terms