The underlined word "event" in the first paragraph refers to______.

A．it will be faster and cheaper than manual labor
B．it can climb mountainsides, drill holes, insert bars and cement
C．it can collect data on the slope's stability
D．it can drill without a human being on board

A．to tell people how serious the damage caused by landslides is
B．to tell people that sending workers to stabilize mountainsides is a risky job
C．to introduce a product that can be used to stabilize mountainsides
D．to show people how to use a new robot