Algebra 1

$F$
Apply power rule of exponents: $(p^a)^b=p^{ab}$ $(3m^2n^4)^3=(3)^3(m^2)^3(n^4)^3$ $=27(m^{2 \times 3})(n^{4 \times 3})$ $=27m^{6}n^{12}$ Hence, the correct answer is $F$.