Natural resources are materials made right from nature and then turned into products that we use in our manufacturing.

单项选择题We have an obligation to maintain the environment, as we depend on the resources and services it provides.

多项选择题对聚类结果进行评估可以采用轮廓系数，它综合考虑了____。 A. 簇内凝聚度 B. 簇内分离度 C. 簇间分离度 D. 簇间凝聚度