First, the statement seems to have an error. The right polynomial must be 16x^3 + 28x^5y.
With that said, we have to find the greatest common divisor of the coefficients and take the common letter with its minimum exponent.
Greatest common divisor of 16 and 28 is determined by facoring both numbers and taking the common factors raised to the minimum power.
16 = 2^4
28 = 2^2 * 7
So, the common factor with the minimum power is 2^2 =4
The common letter with its minimum power is x^3.
So the GCF is 4x^3, i.e. option A)
