What should an Architect recommend to prevent data duplication in salesforce?

Universal Containers has just purchased large volume of contact data from an external vendor. The head of sales would like to use the new data set within the existing production org. The production org currently contains a large volume of contacts.

What should an Architect recommend to prevent data duplication in salesforce?
A . Load the data into salesforce and then utilize the contact Duplicate Rule feature
B . Utilize an off-platform de-duplication tool prior to loading.
C . Create a de-duplication trigger before loading the data.
D . Utilize a batch apex process to de-duplicate the data after loading.

Answer: B