The value of the config/placeholders/ [placeholder_id] /block node from the merged cache.xml configuration is
used______________.

A.
only as a human-readable attribute to the placeholder tags in full page cache records

B.
to fetch the cache lifetime for the full page cache entry from the correct block instance

C.
to build the unique cache id for full page cache records

D.
to map a block instance to the corresponding placeholder configuration while saving a full page cache entry