单选题
The most convincing evidence for the importance of adult influence on a child's intelligence comes from a study of "at risk" children. Ramey and Frances Campbell of the University of North Carolina 61 with children born into poverty-line households. The children entered the study by four months 62 age. During the study, one group spent the day in a center where teachers used games and songs to 63 the infants. Another group had no such 64 , but they were given nutritional supplements in 65 . During preschool years the children in the early-education group showed IQ advantages often to 20 points. The highest-risk children showed the 66 gains, and at age 15 they had higher reading and math scores. What 67 for these gains? Ramey and other scientists say early childhood experiences 68 brain growth. An infant is bom 69 billions of brain cells called neurons. Some are wired to other cells before birth to regulate the 70 of life, such as heartbeat and breathing. Others are waiting to be wired to 71 him or her interpret and respond to the outside world. Experience dictates the hookups. As the child 72 , cells reach out and set up pathways to other cells needed to determine a 73 . For instance, the neurons in the eye send branches to the 74 cortex, which interprets 75 eye sees and, via other branches, 76 the person to react to what is seen. Each time an experience is repeated, the 77 are strengthened. The first two years of life are an explosion of brain 78 and connections. By age two the 79 has more than 300 trillion connections. At the same time, cells that aren't being connected or used are being 80 .
单选题
A. contrast B. addition C. infancy D. abundance
【正确答案】
A
【答案解析】[解析] 四个选项的意思分别是：in contrast相反地；in addition另外：in infancy婴儿期； in abundance大量地，充足。根据语境“but they were given nutr。itional supplements”，很明显 有转折之意：另外一组的孩子补充营养以作对比。四个选项中只有A选项有此意，所以正确 答案是A选项。