Final answer:
The correct answer is b) Door in the face technique. The door in the face technique is a persuasive strategy in which a larger request is made initially, followed by a smaller, more reasonable request.
Step-by-step explanation:
The correct answer is b) Door in the face technique. The door in the face technique is a persuasive strategy in which a larger request is made initially, followed by a smaller, more reasonable request. The sales manager's initial request for a higher amount for the trade-in is the larger request, followed by the smaller request of $21,000 for the new car. This technique is used to make the smaller request seem more reasonable and appealing to the customer after they have rejected the larger request.