#### Answer

$2a$

#### Work Step by Step

The greatest common factor of a group of terms is the greatest factor that evenly divides into all terms in the group.
In this case, $2a$ is the greatest common factor, because it is the largest factor that divides evenly into all 3 terms.
$4a^{2}\div2a=2a$
$6a\div2a=3$
$2a^{3}\div2a=a^{2}$