We’re conducting a nationwide survey of people’s reading habits. Would you have five minutes ________ a few questions?         

A．answering

B．to answer

C．to have answered

D．having answered

（）是指可能导致伤害或疾病、财产损失、工作环境破坏或这些情况组合的根源或状态。

A．事故

B．事件

C．危险源

D．风险