阅读下列材料，从每题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题纸上将该选项标号涂黑。
A
Location
St Helena is one of the remotest islands on Earth. The subtropical（亚热带的） British Overseas Territory sits in the middle of the South Atlantic Ocean, 1, 200 miles from the west coast of Africa and 1, 800 miles from the east coast of South America.
Size Population
St Helena is only 16 km long and 9 km wide and the population is 5, 000. This is 1/3 the size of the Isle of Wight, and the same size as Disney World Orlando. This is also the same size as San Francisco-yet the island has just 0. 5% of San Francisco's population. With an extremely low-crime community, you can freely explore the island's natural and built attractions in peace.
Climate
As a subtropical island, St Helena's temperature is 15 -28°C all year round. While the four seasons are not recognized on St Helena, the "cooler months" are generally June to September and the "hotter months" are December to March. St Helena is free from extreme weather events, with even thunderstorms only occurring perhaps once a decade.
Accessibility
Until 2017, St Helena did not have an airport and was only accessible by sea. Reaching the island meant a five-day ship voyage from Cape Town, South Africa. However, since October 2017, the island's first and only airport has enabled passengers to reach the island in just a six-hour flight.
21. In what aspect are St Helena and San Francisco alike?
A. Area. B. Population. C. Climate. D. Crime rate.
22. What can best describe the climate of St Helena?
A. Tropical. B. Dry. C. Extreme. D. Mild.
23. How could visitors gain entry into St Helena before 2017?
A. By plane. B. By ship. C. By car. D. By bike.
