ANSWER:
2nd option: A customer who is 38 years old buys used car
STEP-BY-STEP EXPLANATION:
Sammy made that conjecture because 6 people under the age of 35 bought only used cars and one couple over the age of 35 bought a new car.
This is false because if only one person under the age of 35 buys a new car or the case where someone over 35 buys a used car, his conjecture makes no sense.
Therefore, the correct answer is:
2nd option: A customer who is 38 years old buys used car