题目

Until the 1960's, almost everyone in the U. S. followed tradition and gave all the children in the same family the same last name or surname, as it is called. But during the 60's, young parents began giving their children strange names—names like Moonglow, Eternal Peace, and Sunshine. Some states passed laws controlling the names that parents could use. But after a court case in 1981, a federal judge ruled that parents are free to give any surnames they wish to their children. So , for the last few decades , more parents are not giving their children the fam­ily 's sur- names .Some insist t用凸透镜在光屏上得到火焰的像，如果用黑纸遮住凸透镜的下半部，屏上的像：A．上半部分没有了B．下半部分没有了 C．无任何变化 D．依然完整，亮度减弱