As people grow older, the ___ of learning declines?

Correct Answer: B. Speed

This option reflects the widely observed phenomenon that as people age, the speed at which they acquire new information and skills tends to decline. This decline in learning speed can be influenced by various factors such as changes in cognitive processing abilities, attentional resources, and working memory capacity. Therefore, the most accurate option in this context is “B. Speed,” as it reflects the common understanding that the speed of learning tends to decline with age.