Which solution should the data architect use to reduce the amount of returned mails?

NTO has been using salesforce for sales and service for 10 years. For the past 2 years, the marketing group has noticed a raise from 0 to 35 % in returned mail when sending mail using the contact information stored in salesforce.

Which solution should the data architect use to reduce the amount of returned mails?
A . Use a 3rd party data source to update contact information in salesforce.
B . Email all customer and asked them to verify their information and to call NTO if their address is incorrect.
C . Delete contacts when the mail is returned to save postal cost to NT
E . Have the sales team to call all existing customers and ask to verify the contact details.

Answer: A