Answer:
D. -m^2n
Step-by-step explanation:
When given a monomial, you can only combine it with like terms. Since the monomial given is 5m^2n, the variable m must be raised to the second power and the variable n must be raised to the first power for it to be a like term.
Answer A is eliminated since m is not raised to the second power. Answer B is eliminated because m is not raised to the second power and n is not raised to the first power. Answer C is eliminated n is not raised to the first power.
