Answer: The third one.
Explanation:
A translation of six units down will change the value of the y-coordinate. In this case, you would take the y-coordinates of each point and subtract by 6 units. Your x-coordinate values will not change. The first option and the last option can automatically be omitted due to a change in the value of the x-coordinate. The second option shows a translation of 6 units UP, so the right value changed, but not the right way.
The third option has a 6 unit decrease in the y-coordinate, along with no change to your x-coordinate, making C) your correct answer.