The common factor is such the a term on which all the terms of the polynomial can be divided. If a term can be taken out common from the entire expression, it is said to be the common factor.
The given expression is 9x - 27. We can take out 9 as common from both terms. The expression becomes:
9 ( x - 3)
So, 9 is the common factor.
Thus the correct answer is option D
