在一密闭容器中，有甲、乙、丙、丁四种物质，在一定的条件下，充分反应，测得反应前后各物质质量如下表

关于此反应，下列认识正确的是 [ ]

A．该变化的基本反应类型一定是置换反应

B．参加反应的甲、丙的质量比为1：9

C．乙、丁的相对分子质量比一定为10：9

D．甲反应后的质量为89

In his effort to prevent his company from _____, he worked to his limit, thus _____.  [ ]

A. breaking down; breaking down his health    

B. closing down; broke down his health 

C. closing down; his health broke down        

D. breaking down; his health breaking down