Concept:Memory retention duration distinguishes types of memory; short-term memory holds information for about 20–30 seconds without rehearsal.Explanation:The brain's memory system is divided into sensory, short-term, and long-term. Short-term memory (also called working memory) temporarily stores a small amount of information for a brief period, typically 20–30 seconds. Unlike long-term memory, which can last a lifetime, short-term memory decays quickly unless rehearsed. Active memory and rote memory are not standard classifications for this timeframe. Therefore, the memory that retains information for 20–30 seconds is short-term memory.Answer:B. Short term memory