Some scientists have suggested that Earth is a kind of zoo or wildlife () for intelligent space beings, like the wilderness areas we have set up on earth to allow animals to develop naturally while we observe them.

A. conservation

B. maintenance

C. storage

D. reserve

各年折旧基数不变但折旧率逐年递减的固定资产折旧方法是( )。

A．平均年限法
B．工作量法
C．双倍余额递减法
D．年数总和法