7、sheer diversity of tropicalplants represents aseemingly______source of raw materials, of which only afew havebeenutilized. (A)exploited (B)quantifiable (C)controversial (D)inexhaustible (E)remarkable 分析:空格填入一个形容词,表示对原材料资源的修饰,并且和热带植物有关。represents表达前后因果关系,所以空格要