题目

我国的下列矿产资源中，具有世界性优势的是 ①铁矿  ②煤矿  ③稀土矿  ④汞矿  ⑤钨矿 A．①②                      B．③⑤                       C．④⑤                      D．①④⑤ 答案：DWe have been good friends __________ we joined the music club. A. before           B. since             C. until