Final answer:
In late adulthood, vocabulary acquisition is an activity that is most likely to improve.
Step-by-step explanation:
According to research, vocabulary acquisition is an activity that an older adult is most likely to improve with age. While other cognitive abilities, such as reaction time, short-term memory, and processing speed, tend to decline in late adulthood, vocabulary acquisition remains relatively stable or even improves. Engaging in mentally stimulating activities, such as reading, learning new words, and engaging in discussions, can help older adults maintain and improve their vocabulary skills.