Final answer:
When trading in a used car, it is best to make the trade-in deal a separate transaction from the new car deal to negotiate and understand the value of the trade-in independently. The correct option is C.
Step-by-step explanation:
When considering trading in a used car when purchasing a new one, it is best to make the trade-in deal a separate transaction from the new car deal. This allows you to negotiate and understand the value of your trade-in separately and avoid any confusion or manipulation by the dealer.
By separating the transactions, you can also explore other options such as selling the car yourself to get a better price rather than relying on the dealer's appraisal.
Hence, Option C is correct.