The most intensive period of speech and language development for humans is during the first three years of life, a period when the brain is developing and maturing. These skills appear to develop best in a world that is rich with sounds, sights, and consistent（一致的，协调的，相容的）exposure（揭发）to the speech and language of others.
There is increasing evidence suggesting that there are "critical periods" for speech and language development in infants and young children. This means that the developing brain is best able to absorb a language, any language, during this period. The beginning signs of communication occur during the first few days of life when an infant learns that a cry will bring food, comfort, and companionship. As they grow, infants begin to sort out the speech sounds (phonemes) or building blocks that compose the words of their language. Research has shown that by six months of age, most children recognize the basic sounds of their native language
As the speech mechanism (jaw, lips, and tongue) and voice mature, an infant is able to make controlled sound. By six months of age, an infant usually babbles or produces repetitive syllables such as "ba, ba, ba" or "da, da, da." By the end of their first year, most children have mastered the ability to say a few simple words. Children are most likely unaware of the meaning of their first words, but soon learn the power of those words as others respond to them.
By eighteen months of age, most children can say eight to ten words. By age two, most are putting words together in crude sentences such as "more milk." During this period, children rapidly learn that words symbolize or represent objects, actions, and thoughts. At this age they also engage in representational or pretend play. At 
ages three, four, and five, a child's vocabulary rapidly increases, and he or she begins to master the rules of language.
1．According to the passage, which of the statements is NOT true
A．The developing brain is best able to absorb any language.
B．The beginning signs of communication occur during the first few days of life.
C．By six months of age, all children recognize th
e basic sounds of their native language.
D．By 2, children rapidly learn that words symbolize or represent objects, actions, and thoughts.
2．We can infer from the passage that____
A．by six months of age, an infant must babble or produce repetitive syllables
B．by their first year, most children are most likely aware of the meaning of their first words
C．by 2, children rapidly learn that words symbolize or represent objects, actions, and thoughts
D．the brain development is critical to develop children’s speech and language ability
3．That there are “critical periods” for speech and language development in infants and young children means ______
A．that children are so young that it is easy for them to study
B．that the developing brain is best able to absorb a language, any language
C．that the children are eager to learn the language
D．that we must take care of children
4 In Paragraph 3, the underlined word “mechanism” can be replaced by ______.
A．organs B．skills C．abilities D．habits
