A、To carry out a scientific survey. B、To establish a new research station. C、To rescue two sick American workers. D、To deliver u

A small plane with two sick US workers arrived safely in Chile late Wednesday after leaving Antarctica in a daring rescue mission from a remote South Pole research station. After making a stop for a few hours at a British station on the edge of Antarctica, the two workers were flown to the southernmost Chilean city of Punta Arenas. In a chaotic two days of flying, the rescue team flew 3,000 miles round-trip from the British station Rothera to pick up the workers at the US Amundsen-Scott station at the South Pole. "The two patients aboard will be transported to a medical facility that can provide a level of care that is not available at Amundsen-Scott," says a spokesperson. Normally planes don’t go to the polar post from February to October because of the dangers of flying in the pitch-dark and cold. "Antarctica creates a hostile environment," says the operations director for the British Antarctic Survey. "If you’re not careful, it’ll come round and bite you."
3. What was the small plane’s mission to Antarctica?
4. What makes flying to Antarctica dangerous from February to October?