Answer is D
Deleted custom fields and their data are stored until your org permanently deletes them or 15 days has elapsed, whichever happens first. Until that time, you can restore the field and its data.
Surely not A as The data in the field is stored for 15 days.

Ans is B

This message shows when I try to delete the field:
Deleting a custom field will:

Delete all dependent information for any dependent or controlling field
Change the result of Assignment or Escalation Rules that rely on the custom field data
In order to preserve a record of data for future reference, run a data export before deleting custom fields by clicking Data | Data Export.

After you've deleted this field, it appears in the deleted components list for 15 days. During that time, you can either undelete it to restore the field and all data stored in it, or delete the field permanently. Note that when you undelete a field, some properties on the field will be lost or changed. After 15 days, the field and its data are permanently deleted.

You will have 15 days to undelete this field to restore the field and all data stored in it, and after that time it and all data stored in it will be automatically permanently deleted.

So, i think that B is the correct, cause the messge shows this:"In order to preserve a record of data for future reference, run a data export before deleting custom fields by clicking Data | Data Export." that prevents the data loss....

Its B. D it’s not the one because the data is not restored from the bin, in case is restored it would be restored from setup/fields&relationships ina button on the top next to field dependencies

I mean B or D.

If data can be restored, it would be restored from the recycle bin in 15 days. Therefore A is wrong. All field history data would be deleted (standard or custom object) so I think this rules out C since it makes no sense, therefore the answer is B or D. I'm finding mixed articles about whether custom fields can be restored or not. This SF article says yes, therefore the answer would be D, but other articles says the data is permanently deleted.

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

The answer should be D. The issue with A is that Salesforce only stores the data for 15 days, NOT 20. From Salesforce Help article: "Deleted custom fields and their data are stored until your org permanently deletes them or 15 days has elapsed, whichever happens first. Until that time, you can restore the field and its data."

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

Wrong, answer is B or C