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.
正确答案：D
答案解析：最后一段讲到加勒比海的天气温暖，阳光充裕，许多岛屿的海岸有沙滩。这样的自然环境显然会吸引旅游者。因此D是正确的选择。这里也可以根据关键词tourists来解题。