题目

辽宁省开原市六校2011届高三上学期第一次联考 Barack Obama delivered a speech to 500 local youths during his visit to China, many of ____ from Fudan University and Tongji University．        A．them B．whom       C．which   D．who    答案：A   下面的计算正确的是（　　）A．a4?a3=a12B．（a+b）2=a2+b2C．a3?a7÷a5=a2D．（-x+2y）（-x-2y）=x2-4y2