After analyzing imaging scans collected over 17 years，researchers had found that the brain of highly intelligent children develop in a different pattern from those with more average abilities．

      The discovery，some experts said，could help scientists understand intelligence in terms of the genes that develop it and the childhood experiences that can improve it．“This is the first time that someone has shown that the brain grows differently in extremely intelligent children，”said Paul Thompson，a brain―imaging expert at the University of California in Los Angeles．

      The finding is based on 307 children in Bethesda，Maryland．Starting in 1 989，they were given regular brain scans using magnetic resonance imaging（磁共振成像）．The general pattern of maturation（成熟），they reported on Thursday in Nature，is that the cortex（皮層）grows thicker as the child ages and then thins out．The causes of the changes are unknown，because the imaging process cannot see down to the level of individual neurons（中子）．

      The researchers found that average children（IQ scores 83 to 108）reached a peak of cortical thickness at age 7 or 8．Highly intelligent children（121 to 149 in IQ）reached a peak of thickness much later，at 13．One explanation is that the brains of highly intelligent children are more changeable，swinging through a higher trajectory（軌道）of conical thickening and thinning than occurs in average children．

      Thompson said the new study opened up huge possibilities because researchers should be able to find the factors that influence the brain by looking at the scan patterns found by the researchers．The Bethesda children have had genetic samples taken from their cells，so genes that have even the smallest influence on the brain should be discovered．The pattern of development can also be affected by factors like diet，hours spent in school or the number of children in their families，and these may come to light by asking parents how they raised their children．

71．According to the passage，what factors may not affect the development of a child’s brain pattern?

    A．What kind of diet a child eats．

    B．How much exercise a child does．

  C．How many hours a child spends in schoo1．

  D．How many children there are in the family．

72．What does the underlined word“it”in the second paragraph refer to?

    A．The discovery．      B．The pattern．        C．Intelligence．          D．Influence。

73．According to the passage，which of the following statements in NOT true?  

    A．People didn’t know whether intelligent children’s brains grow differently from average children’s before the discovery．

    B．As a child grows older，the brain cortex grows thicker and then thins out．

    C．There is the possibility that researchers will know what influences the development of brain in the future．

    D．The researchers has found out why the brain’s general pattern has changed．

74．Why did highly intelligent children reach a peak of thickness much later than average children?

    A．Intelligent children have unusually big brains．

    B．Intelligent children have different childhood experiences．

    C．Intelligent children’s brains ale more likely to change．

    D．Intelligent children’s genes have more influence on the brain．

75．The purpose of the passage is probably to

    A．introduce the result of a scientific study on the brains of intelligent children

    B．illustrate research on the cortical thickness of human brains

    C．explain how the brain works as a child grows older

    D．compare the brain structure intelligent children with that of average children