题目

The companies are working together to create________they hope will be the best means of transport in the 21st century. A．which         B．that         C．what         D．who 答案：C20．如图，点P是抛物线y=-x2+4的顶点，将抛物线平移，平移后的抛物线与x轴交于A，B两点（A在B的左侧）顶点Q落在第一象限内，且△ABQ是等边三角形，直线PQ与x轴交于点C，若PQ=$\sqrt{3}$，则BC=3$\sqrt{2}$-$\sqrt{3}$．