Answer:
The correct answer is letter "C": "To our valued consumers:".
Step-by-step explanation:
Conveying goodwill in writing messages imply stating the reasons why a given party conducted businesses that ended up being harmful. The firm at fault should explain what it was pursuing and why it was not able to expect such an adverse situation. At all moment the message must be formal and highlight the importance of continue doing business with consumers.
Under that scenario, "To our valued consumers:" is the most suitable greeting to use before starting to explain the facts that took place and the course of action the firm will follow.