The number of digits an individual can report back without error in a single presentation represents:

The number of digits reported back without error in a single presentation is the memory span.

Chunking (A) groups items into larger units to expand capacity, not the count itself.

Phonological loop (C) is the verbal store within working memory, not the measured span.

Time zone (D) is unrelated to memory measurement.

Digit span is a common test of short-term memory capacity.

Miller placed short-term capacity at about seven plus or minus two items.