题目

. During the twentieth century there has been a great change in the lives of women. A woman marrying at the end of the nineteenth century would probably have been in her middle twenties, and would be likely to have seven or eight children, of whom four or five lived till they were five years old. By the time the youngest was fifteen, the mother would have been in her early fifties and would expect to live a further twenty years, during which chance and health made it unusual for her to get paid work. Today women marry younger and have fewer children. Usually a woman’s youngest child will be （2011年浙江宁波，16题）下表为科学家通过研究获得的一些信息(“√”表示能够存活，“一”表示不能存活)          pH种类6．5-7．06．0～6．54．5-6．03．0-4．5溪红点鲑√√——小口黑鲈√√——黑头呆鱼 √———牛蛙胚胎√√√—小龙虾√√—— 下列说法错误的是   （ ▲ ）A．该实验研究的是水体pH变化对部分生物的影响B．水体pH为3．0～4．5时，最适合这些生物生存C．上述生物中，牛蛙胚胎在水体pH变化时存活范围最大D．水体pH发生变化可能是由酸雨造成的