如图所示，这是一瓶无色无味的气体，根据你已有的知识经验，对它的成分进行探究：

（1）假设：它是一瓶            气体。

（2）设计实验方案证明你的假设：

步骤：                                                 ；

现象：                                                 ；

结论：                                                 。   

According to the psychoanalyst Sigmund Freud, wisdom comes from the _____ of maturity.

A．fulfillment

B．achievement

C．establishment

D．accomplishment