Cao Min couldn't believe she was experiencing exactly what she had seen years ago in the film "Titanic". Cao and her two children from Anhui Province were traveling on board the "Liaoludu 7" on February 22. They were among the first people on the ship who were rescued by lifeboats. Cao's one-year-old son was the youngest passenger on board. The "Liaoludu 7" was traveling in the Bohai Straits from Lvshun in Liaoning Province to the port city of Longkou in Shandong Province. It suddenly lost its power at 2:30 pm and tilted  on its side. With 81 people on board, the ferry began to sink. "I was so scared that my legs couldn't move forward. They kept shaking even when I was asked to jump onto a lifeboat," Cao recalled. Upon receiving the mayday appeal  , China Marine Search and Rescue Centre immediately informed the State Council. The center sent eight lifeboats to the fishing boats. After more than four hours of fighting strong winds and freezing ocean water, the passengers were recovered. All but four survived. These four died after spending too long time in the freezing waters, according to a spokesperson for the Beijing-based center. According to the passage,   _   passengers on board were still alive.
four seventy-seven eight eighty-one
Question: Cao Min couldn't believe she was experiencing exactly what she had seen years ago in the film "Titanic". Cao and her two children from Anhui Province were traveling on board the "Liaoludu 7" on February 22. They were among the first people on the ship who were rescued by lifeboats. Cao's one-year-old son was the youngest passenger on board. The "Liaoludu 7" was traveling in the Bohai Straits from Lvshun in Liaoning Province to the port city of Longkou in Shandong Province. It suddenly lost its power at 2:30 pm and tilted  on its side. With 81 people on board, the ferry began to sink. "I was so scared that my legs couldn't move forward. They kept shaking even when I was asked to jump onto a lifeboat," Cao recalled. Upon receiving the mayday appeal  , China Marine Search and Rescue Centre immediately informed the State Council. The center sent eight lifeboats to the fishing boats. After more than four hours of fighting strong winds and freezing ocean water, the passengers were recovered. All but four survived. These four died after spending too long time in the freezing waters, according to a spokesperson for the Beijing-based center. According to the passage,   _   passengers on board were still alive.
A. four
B. seventy-seven
C. eight
D. eighty-one
Answer: