Final answer:
The memory type demonstrated during tasks that do not require intentional remembering is implicit memory, which operates without conscious awareness.
Step-by-step explanation:
The type of memory apparent when retention is exhibited on a task that does not require intentional remembering is C) Implicit memory. Implicit memory refers to memories that influence our behaviors or thought processes without our conscious awareness, and involves tasks such as riding a bicycle or driving a car where the performance improves over time without intentional recollection of the learning process. Unlike explicit memory, which includes memories we can consciously recall such as events (episodic memory) or facts (semantic memory), implicit memory operates without our active retrieval of past experiences.