If $A$ denotes the sum of all the coefficients in the expansion of $\left( 1 - 3 x + 10 x ^ { 2 } \right) ^ { n }$ and $B$ denotes the sum of all the coefficients in the expansion of $\left( 1 + x ^ { 2 } \right) ^ { n }$, then:\\
(1) $\mathrm { A } = \mathrm { B } ^ { 3 }$\\
(2) $3 \mathrm {~A} = \mathrm { B }$\\
(3) $\mathrm { B } = \mathrm { A } ^ { 3 }$\\
(4) $\mathrm { A } = 3 \mathrm {~B}$