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Start by looking for the GCF for the coefficients: 12, 6 and -4
largest factor/number that divides out of all of them.
GCF for coefficients is 2
Then take the smallest exponent common to all terms for each variable.
smallest exponent for "a" is 3
smallest exponent for "x" is 2
smallest exponent for "y" is 1
GCF is: 2a³x²y
Answer A.