Factor as Completely as Possible $49 \mathrm { k } ^ { 3 } \mathrm {~m} + 126 \mathrm { k } ^ { 2 } \mathrm {~m} ^ { 2 } + 81 \mathrm {~km} ^ { 3 }$

Multiple Choice

Factor as completely as possible. If unfactorable, indicate that the polynomial is prime.
- $49 \mathrm { k } ^ { 3 } \mathrm {~m} + 126 \mathrm { k } ^ { 2 } \mathrm {~m} ^ { 2 } + 81 \mathrm {~km} ^ { 3 }$

A) $k m ( 7 k - 9 m ) ^ { 2 }$
B) $k m ( 7 k + 9 m ) ^ { 2 }$
C) $k m ( 7 k + 9 m ) ( 7 k - 9 m )$
D) Prime