B & D. Follow the explanation:

Suppose that you want to deploy a custom metadata named MyCustomMetadata and his 2 record named Rec1 and Rec2.
You will need to add in the XML one record in CustomObject section (to add MyCustomMetadata) and 2 record in CustomMetadata section (to add Rec1 and Rec2)

correct answer is B and D

Correct answers should be A and D. Custom Metadata Types are Custom Objects for the Metadata API, and its fields are Custom Fields.

If the Custom Metadata records were deployed too, the CustomMetadata metadata type would be needed.

Take in account the question refers to Metadata API, not Change Sets: https://developer.salesforce.com/docs/atlas.en-us.api_meta.meta/api_meta/meta_custommetadatatypes.htm

A and C are corrects https://trailhead.salesforce.com/ja/content/learn/modules/custom_metadata_types_dec/cmt_create

Rachelle is correct. A and C for sure.

Answers are correct A and C https://help.salesforce.com/s/articleView?id=sf.custommetadatatypes_changesets.htm&type=5

The correct answers are B & D.
Please refer this document https://www.jitendrazaa.com/blog/salesforce/how-to-retrieve-and-deploy-custom-metadata-types-using-ant/