题目

Steve has done his homework _______, but Kathy hasn't done hers_______. A. already, yet      B. already, already        C. yet, yet            D. yet, already 答案：A关于青藏高原的叙述，正确的是（　　）A．位于我国西北部B．平均海拔6000米以上C．是世界上面积最大的高原D．约占全国面积的14