Final answer:
The most rapid developmental changes occur from birth to age 2. During this time, infants experience significant increases in both weight and height, leading to the conclusion that the correct answer is (a) birth to age 2.
Step-by-step explanation:
Individuals experience the most rapid and dramatic developmental changes during infancy, specifically from birth to age 2. During this period, babies, also referred to as infants, undergo a rapid growth in weight and height, with an approximately 200 percent increase in weight and nearly 100 percent increase in height from birth to one year old. By comparing the information provided with the options given in the question, the answer is (a) birth to age 2, which is when the growth and development are the most rapid.
Additionally, the frontal lobes of the brain are not fully developed at birth. They continue to develop and are not fully mature until around 25 years of age. So, the significant cognitive and psychosocial development also occurs later in the lifespan during adolescence and early adulthood.