Option A
The greatest common factor is 4ab
<em><u>Solution:</u></em>
Given that,
We have to find the greatest common factor

<em><u>First find the GCF of numbers</u></em>
GCF of 12, 20, 16
The factors of 12 are: 1, 2, 3, 4, 6, 12
The factors of 16 are: 1, 2, 4, 8, 16
The factors of 20 are: 1, 2, 4, 5, 10, 20
Then the greatest common factor is 4
<em><u>Now find the GCF of variables</u></em>

Here,
ab is the greatest common factor
Therefore, GCF of variables is ab
Thus, GCF of given expression is: 4ab