一件商品的原价是100元，经过两次提价后的价格为121元，如果每次提价的百分率都是x．根据题意，可列出方程为：______．

Many lifestyle patterns do such ________ great harm to health that they actually speed up ________ weakening of the human body．[ ]

A．a；/  

B．/；the  

C．a；the  

D．/；/