生活在沙漠中的仙人掌，叶退化成刺可以减少水的散失．对此最恰当的解释是（　　）

A．生物影响环境

B．生物适应环境

C．生物改变环境

D．生物依赖环境

They had to ______ the meeting because the organizers didn’t prepare the hall well, where people can share their opinions and hold discussions. 

A．put forward

B．put out

C．put up

D．put off