Answer:
B.
Explanation:
A and C have awkward sentence structure because "when a car needs many serious repairs, it might be cheaper to buy a new car", it repeats the word car again making it redundant and in C, "When a car had needed many serious repairs, it might be cheaper to buy a new one", it has wrong use of past-tense.
Answer:
B. When a car needs many repairs, it might be cheaper to buy an new one.
Explanation:
