Final answer:
The 'bank' that David slides down is metaphorically referring to a memory bank, considering the context of the reference provided which emphasizes memories and experiences.
Step-by-step explanation:
The question refers to a metaphorical 'bank' that David slides down, mentioned in a poetic or literary context. In this case, considering the provided reference which talks about a heap of frozen images and memory being accentuated, the most appropriate answer to what the 'bank' could be is D. a memory bank. The excerpt speaks metaphorically about memories being akin to a winter landscape and evokes a sense of a collective memory or recollection of events, which is comparable to a memory bank where experiences and information are stored.