Answer:
They include good and service guarantees (D)
Explanation:
Option A . This false. Focusing on gaining new customers is part of pre-production services because this yet to be turned to sales.
Option B. This is false. Contract negotiation is part of pre-production services because it is a deal that is yet to be concluded.
Option C. This is false.
Option D.This is true. It is part of post-production services such after sales service.