Final answer:
Crystallized intelligence may stay steady or improve with age, while fluid intelligence usually decreases in late adulthood. Mental and physical activities can help slow the decline of cognitive abilities.
Step-by-step explanation:
Changes in Mechanics of Intelligence in Adulthood
Intelligence in adulthood can be divided into crystallized intelligence and fluid intelligence. Crystallized intelligence consists of knowledge and skills accumulated over a lifetime and tends to remain steady or even improve into late adulthood. On the other hand, fluid intelligence, which involves the ability to see complex relationships and solve problems, often begins to decline in later adulthood. Staying mentally and physically active can help delay cognitive decline and reduce the incidence of cognitive impairments.
With respect to the changes in mechanics of intelligence in adulthood, the correct option would be that fluid and crystallized intelligence both decrease as it's generally agreed that while crystallized intelligence can remain steady or increase with age, fluid intelligence typically decreases in late adulthood.