Fifteen people were killed and 38 others injured in a road accident early Wednesday morning in Ens hi, Central China's Hu bei Province. The bus, travelling from Wanzhou in Southwest China's Chongqing Municipality to  Shen zhen in South China's Guangdong Province, had 53 _ on board,three more than permitted. At around 1 am on Wednesday, the bus increased speed gradually on a curve and plunged  more than 30 metres into a valley below. Thirteen people, including one of the two drivers, died at once. Two others died on the way to hospital. Although the cause of the accident is still unclear, the local police said the driver paid no attention to the official warning signs on the expressway . It hit a section which had been closed as a result of snow. Because of the cold weather and icy roads,the expressway had been closed by police since Tuesday morning. But the bus drivers took the dangerous route, paying no attention to the warnings. The rescue team, which included more than 30 medical workers and 120 local villagers,joined together and rushed to the scene at the news of the accident. By 5 am, all of the injured had been sent to three local hospitals for emergency treatment. A hospital source said most of the patients were in a stable condition but a few were still in danger. According to a 2009 national public opinion poll, traffic accidents ranked as people's third biggest security  concern. The expressway was closed to   _  .
protect the passengers from being frozen make the police have a good rest stop cars traveling around avoid  the happening of traffic accidents
Question: Fifteen people were killed and 38 others injured in a road accident early Wednesday morning in Ens hi, Central China's Hu bei Province. The bus, travelling from Wanzhou in Southwest China's Chongqing Municipality to  Shen zhen in South China's Guangdong Province, had 53 _ on board,three more than permitted. At around 1 am on Wednesday, the bus increased speed gradually on a curve and plunged  more than 30 metres into a valley below. Thirteen people, including one of the two drivers, died at once. Two others died on the way to hospital. Although the cause of the accident is still unclear, the local police said the driver paid no attention to the official warning signs on the expressway . It hit a section which had been closed as a result of snow. Because of the cold weather and icy roads,the expressway had been closed by police since Tuesday morning. But the bus drivers took the dangerous route, paying no attention to the warnings. The rescue team, which included more than 30 medical workers and 120 local villagers,joined together and rushed to the scene at the news of the accident. By 5 am, all of the injured had been sent to three local hospitals for emergency treatment. A hospital source said most of the patients were in a stable condition but a few were still in danger. According to a 2009 national public opinion poll, traffic accidents ranked as people's third biggest security  concern. The expressway was closed to   _  .
A. protect the passengers from being frozen
B. make the police have a good rest
C. stop cars traveling around
D. avoid  the happening of traffic accidents
Answer: