Explanation:

A. Add only ❌
This import operation appends new records to the Data Extension but does not update existing records or remove any records that are missing from the file. If a record already exists in the Data Extension, it will remain unchanged, and any records not in the file will still exist in the DE after the import. This is not the behavior desired in this scenario since the requirement is to also remove records not present in the CSV. Therefore, this is not the correct choice.

B. Overwrite ✅ (Correct Answer)
The "Overwrite" import option completely replaces all data in the target Data Extension with the data from the imported file. This means that any records not included in the CSV file will be removed from the Data Extension, and the existing records will be replaced with the new version. This perfectly matches the scenario where only the records in the file should remain in the Data Extension after the import. It's the best fit for a full data sync when the file is authoritative.

C. Add and update ❌
This operation will add new records and update any matching existing records based on the primary key but will not remove records that are missing from the import file. It is ideal when your CSV includes partial data and you want to supplement or correct the DE without deleting anything. However, since the scenario explicitly says that records not in the file should be removed, this operation would not meet the requirement.

D. Update only ❌
This option updates records that already exist in the Data Extension (based on primary key match) but does not add new records or remove any that are not present in the import file. In this case, since the file contains all relevant data, we must be able to add new rows and remove others — which this option does not support. Thus, it's not suitable for this scenario.