Answer:
D. At 18, people are more mature and better able to make mature decisions.
Step-by-step explanation:
A supporting point is a detail of information that provides a proof or evidence of the writer's opinion or idea in a text. Such information should be relevant to the topic and should also be helpful in proving his side.
Among the choices above, letter D is the BEST supporting point to defend the author's position. For him, 18 is a better age for driving because the person is more mature. Thus, this is supports the idea on why teenagers should only be allowed to get a driver's license once they are 18 years old already.
So, this explains the answer.