单选题
【填句补文】The weather of the Caribbean Sea is almost always warm and sunny．Sandy beaches line the coasts of many islands. ________. Many tourists arrive on cruise ships.
A、They are Cuba，Puerto Rico，Jamaica，and Hispaniola.
B、The Caribbean Islands are known by several names.
C、Some of these islands are no more than tiny slivers（小片）of exposed coral.
D、This is why millions of tourists visit the islands each year.