Final answer:
The first years of life are crucial for language and speech development because the brain has a natural ability to acquire language during this period. Babies learn language through exposure and progress through stages of language learning.
Step-by-step explanation:
The first years of life are the most important time for language and speech development because the brain is specially equipped to learn language during this period. Babies have a natural ability to acquire language, which allows them to learn through exposure to their environment. This rapid process of language learning takes place between the ages of nine months and three years, and babies progress through stages that enable them to learn language just by being surrounded by speech.