The answer is D. Per Salesforce Help article: "When you delete a custom field, all of the field history data is deleted and changes are no longer tracked."

https://help.salesforce.com/s/articleView?id=sf.deleting_fields.htm&type=5

D is the right answer not B or C because that needs to be done if page layout or report is modified in between when the field was deleted

Am confused cos the salesforce document mentions the follows:

Add the field to any page layouts that changed during the time the custom field was deleted. If reports and page layouts were not edited, the restored field remains on them.

So either you have to add to page layout or to the report. Ideally Option B and C both are correct.

The right answer is C. Please review this documentation: https://help.salesforce.com/s/articleView?id=sf.fields_manually_restore_attributes.htm&type=5