For the system of equations below, which method is most efficient and why? $$ \begin{cases} 4a - 5b = 12 \\ -4a + 3b = -8 \end{cases} $$

Substitution, because one equation is already solved for a variable.

Elimination, because the coefficients of the variable $a$ are opposites.

Substitution, because the constant terms are 12 and -8.

Elimination, because the coefficients of the variable $b$ are the same.

Which characteristic of a system of linear equations most strongly suggests using the elimination method?

One equation is already solved for one variable.

Both equations are in standard form ($Ax+By=C$) and the coefficients of one variable are opposites.

The constant terms in both equations are identical.