语法填空（共10小题；每小题1.5分，满分15分）
阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填人一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡标号的相应位置上。
In this unlikely place, researchers are putting the seeds from flowering plants and trees in a sleeplike state. Many years from now, other workers will wake the sleeping seeds up to plant them
1 they are most needed. These seeds are 2 the legendary Rip Van Winkle, who fell asleep under a tree and woke up 20 years later.
The small farm, called the Greenbelt Native Plant Center, is part of a global effort to save 3 (threaten) plants and trees. Around the world, native plants are being crowded out by invasion newcomers. Native plants have less room to grow now 4 a result of the growth and spread of cities. And global warming is making some places hotter, drier, or different from 5 native plants are used to.
Experts used to think 6 possible to protect big-city plants such as American bittersweet because growth space is limited in urban environments. Crowding increases competition between natives and invaders, and the latter often win the battle.
7 , scientists have found ways 8 fighting back. So far, workers at the Greenbelt Native Plant center 9 (gather) seeds from about 300 of those plants and put them in a sleeplike state. When 10 (plant) in the future ,these seeds could help restore damaged parkland and forests.