Add the Polynomials $7 x + 12,9 x ^ { 4 } + 4 x + 12 \text { and } 10 x ^ { 4 } - 6 x + 15$

Add the polynomials. $7 x + 12,9 x ^ { 4 } + 4 x + 12 \text { and } 10 x ^ { 4 } - 6 x + 15$

A) $21 x ^ { 4 } + 5 x + 44$
B) $19 x ^ { 4 } + 8 x + 44$
C) $19 x ^ { 4 } + 5 x + 39$