medium rank bitumite

例句：

1. 1. The medium-rank bitumite is a valuable resource for road construction.
   中等等级的沥青岩是道路建设的重要资源。
2. 2. The engineers used the medium-rank bitumite to improve the durability of the roads.
   工程师们使用了中等等级的沥青岩来提高道路的耐用性。
3. 3. The medium-rank bitumite was extracted from deep in the earth, and its properties were studied extensively.
   中等等级的沥青岩是从地下深处提取出来的，其性质得到了广泛的研究。