题目

He made up his mind to devote his life ____ pollution _____ happily.  A. to prevent, to live                   B. to prevent, from living   C. to preventing, to live                 D. to preventing, living 答案：C15．如图，在由六个全等的正三角形拼成的图中，菱形的个数为（　　）A．3B．4C．5D．6