Simplify the Expression $-7 \mathrm{k}^{2 / 7}\left(-4 \mathrm{k}^{3 / 7}+9 \mathrm{k}^{6 / 7}\right)$

Multiple Choice

Simplify the expression. Write answer with positive exponents. Variables are positive real numbers.
- $-7 \mathrm{k}^{2 / 7}\left(-4 \mathrm{k}^{3 / 7}+9 \mathrm{k}^{6 / 7}\right)$

A) $-11 \mathrm{k}^{5 / 7}-16 \mathrm{k}^{8 / 7}$
B) $28 \mathrm{k}^{5 / 7}+63 \mathrm{k}^{8 / 7}$
C) $28 \mathrm{k}^{-1 / 7}+63 \mathrm{k}^{-4 / 7}$
D) $28 \mathrm{k}^{5 / 7}-63 \mathrm{k}^{8 / 7}$