Universal containers regularly imports accounts from an external order system that has its own id field for each record. what should the system administrator do to prevent duplicates during these imports?
a. use the id from the order system in place of the sfdc idb. create a unique external id field on accounts in sfdc for matching. c. use vlookup to find matching records in sfdcd. create a formula field that identifies matches.

B. Create a unique External ID field on Accounts in SFDC for matching.                                      

Explanation:

External ID is used to prevent duplicate records from being created as a consequence of the import operation, when importing custom objects or person accounts.An external ID is a specific field that contains the External ID attribute.External ID has unique record identifiers from a system that is outside the Salesforce.When this option is selected Data Import Wizard identifies existing Salesforce records with external IDs that match the values in import file.The External ID field enables to keep unique record IDs from an external system, usually for integration. External ID field values should be unique and determine whether or not value are case sensitive can also be determined. For example XYZ and xyz will not be considered same if case sensitive option is not selected.