Intracoronal retainer placed in the abutment teeth has the following disadvantage: (A) It is unaesthetic, (B) They cannot provide support and stability, (C) Difficult laboratory procedure, (D) Difficult to repair and replace
Answer is D. Internal or precision attachments
Advantages:

Improved aesthetics, by elimination of a visible retentive component and vertical support.

Disadvantages:

Difficulty in repair and replacing.
Greater cost to the patient.
Inability to use in teeth having short clinical crowns and tissue-supported distal extension denture bases.