【改编】Is language, like food, a basic human need without which a child at a critical period of life can be starved and damaged? Judging from the experiment of Frederick in the thirteenth century, it may be. Hoping to discover what language a child would speak if he heard no mother tongue, he told the nurses to keep silent.
All the infants died before the first year. But clearly there was more than lack of language here. What was missing was mothering. Without good mothering, in the first year of life especially, the capacity to survive is seriously affected.
Today no such severe lack exists as that ordered by Frederick. Nevertheless, some children are still backward in speaking. Most often the reason for this is that the mother is insensitive to the signals of the infant, whose brain is programmed to learn language rapidly. If these sensitive periods are neglected, the ideal time for acquiring skills passes and they might never be learned so easily again. A bird learns to sing and to fly at the right time, but the process is slow and hard once the critical stage has passed.
Experts suggest that speech stages are reached in a fixed order and at a constant age, but there are cases where speech has started late in a child who eventually turns out to be of high IQ. At twelve weeks a baby smiles and makes vowel-like sounds; at twelve months they can speak simple words and understand simple commands; at eighteen months he has a vocabulary of three to five words. At three he knows about 1,000 words, which he can put into sentences, and at four his language differs from that of his parents in style rather than grammar.
Recent evidence suggests that an infant is born with the capacity to speak. What is special about man’s brain, compared with that of the monkey, is the complex system which enables a child to connect the sight and feel of, say, a toy-bear with the sound pattern “toy bear”. And even more incredible is the young brain’s ability to pick out an order in language from the mixture of sound around him, to analyze, to combine and recombine the parts of a language in new ways.
But speech has to be induced（激发，引起）, and this depends on interaction between the mother and the child, where the mother recognizes the signals in the children’s babbling（咿呀声）,grasping and smiling, and responds to them. Insensitivity of the mother to these signals dulls the interaction because the child gets discouraged and sends out only the obvious signals. Sensitivity to the child’s nonverbal signals is essential to the growth and development of language.
The experiment of Frederick proved ____.

A．lack of mothering didn’t affect the development of a baby

B．only lack of language could kill a baby

C．very cruel to the babies in the experiment

D．babies could be starved to death

Why are some children backward in speaking?

A．Because they are born disabled.

B．Because they lack language input when in sensitive periods.

C．Because they are exposed to too much language at once.

D．Because their mothers are not smart enough

Which of the following is true ?

A．If a child starts to speak later than others, he will be backward in future.

B．If the ideal time for acquiring skills passes, there will be a second time.

C．A child can only imitate others’ language.

D．An infant is born with the ability to speak.

What is the purpose of the example of birds in the third paragraph?

A．To prove the importance of the sensitive periods.

B．To prove birds has the same ability to speak as human.

C．To explain why some birds can’t sing.

D．To inform the results of Frederick’s experiment.

where can you read this passage?

A．In a science report.

B．In an Entertainment magazine.

C．In a health report.

D．In a science fiction story.