Islands are geographical formations that are completely surrounded by water, yet many islands are covered with a rich assortment of plant life. It may seem surprising that so much plant life exists on many islands, yet there are surprisingly simple explanations as to how the vegetation has been able to establish itself there. Some islands were formerly attached to larger bodies of land, while others were created on their own. Islands that were created when flooding or rising water levels cut them off from their neighbors often still have the plant life that they had before they were cut off. In cases where islands formed out of the ocean, they may have plant life from neighboring lands even though they were never actually attached to the neighboring lands. Winds carry many seeds to islands; some plants produce extremely light seeds that can float thousands of feet above the Earth and then drift down to islands where they can sprout and develop. Birds also carry seeds to islands; as birds move over open stretches of water, they can serve as the transportation system to spread seeds from place to place.

Answer Choices (choose 3 to complete the chart):

(1) Some seeds are able to float great distances in the air.

(2) Some plant life existed before islands were cut off from larger bodies of land.

(3) Some islands have many different varieties of plants.

(4) Birds sometimes carry seeds to islands.

(5) Some islands were created when rising water cut them off from larger bodies of land.

(6) Some plant seeds are carried to islands by the wind.

参考答案：（ 2 ）、（ 4 ）、（ 6 ）