题目

Three boys were enjoying themselves in their hometown of Bovina, Mississippi. However, their lives were turned upside down when they discovered the jawbone of a Mastodon (齿乳象).Brothers Shawn and Caid Sellers and cousin Michael Mahalitc found the prehistoric bone in a piece of earth that was recently plowed (犁、耕). “I thought it was a log,” Caid said. “I tried to pick it up and it was really heavy and I saw teeth on it.” The bone weighed about 50 pounds. They eventually got the bone to their home and fitted it in their tub (浴盆), but it took their collective strength, migh17．欧洲鳗从马尾藻海西南部迁往欧洲，首先借助的洋流属于是（　　）①以副热带为中心的大洋环流   ②以副极地为中心的大洋环流③寒流                                      ④暖流．A．①③B．①④C．②③D．②④