I have got a lot of CDs of the most popular singers. I can't decide _____. [ ]

A. which one to listen to

B. to listen to which one

C. which one should I listen to

D. what I should listen to

（）属于科学认识的“硬件”，即在科学认识活动中进行观察、测量、计算、存储信息的各种物质手段。

A.科学方法

B.科学器材

C.科学探索

D.科学计量