The pair of like terms is 4g and 9g.
Like terms are terms that have the same variable(s) raised to the same exponent(s). In the given options:
4g and 9g: These are like terms because they both have the variable "g" raised to the first power.
gA and h4: These are not like terms because they involve different variables ("g" and "h") and different exponents.
g and gh: These are not like terms because one has the variable "g" and the other has "gh," which is a different term.
3g and 3h: These are not like terms because they involve different variables ("g" and "h").