In the last sentence of the second paragraph, "the higher places on earth" refers to ______.

D
44．答案为D。根据第二段最后一句及第三段第一句，covering its whole surface except for the higher places on earth that had been formed from the lighter rock materials．In 1970，scientists had pieced together evidence that the lighter rock materials had formed one huge continent by a vast ocean可知“较高的地方”不可能指选项B和C；选项A文中未提及。