Final answer:
The correct answer is B, which uses the present tense appropriately to describe the situation where buying a new car might be cheaper than repairing an old one.
Step-by-step explanation:
The correct answer is B: When a car needs many serious repairs, it might be cheaper to buy a new one. This sentence is in the present tense, which is appropriate for discussing a current situation or decision. Comparing options for a car purchase involves assessing potential repair costs against the price of buying new, the warranty coverage, and the reliability of a used vehicle from different sources. The cost-benefit analysis needs to consider the risks of encountering more problems and the associated repairs, which could turn a used car into an expensive proposition.