[解析]
(1)细节理解题。根据第三段Paul then went to college to study the science of plants.(保罗随后进入大学学习植物科学。)可知,保罗在大学时学到了很多关于植物的科学知识。故选B。
(2)词句猜测题。根据第五段And every week,he made his secret journey into the wasteland and planted trees and grass.For fifteen years he did this against the plain common sense.(每周,他都会秘密前往荒地,植树种草。十五年来,他做这件事违背了普通常识。)所以the plain common sense是指"树木不可能在荒地上生长"。故选A。
(3)细节理解题。根据倒第二段Later,as there was legal pressure to clean up the environment,the company actually hired Paul to do what he was already doing.(后来,由于有清理环境的法律压力,该公司实际上雇佣了保罗,让他做他已经在做的事情。)可知,公司雇保罗种树种草是因为他们被迫这么做。故选D。
(4)主旨大意题。根据最后一段It took him until his hair turned white,but he managed to keep that impossible vow he made to himself as a child.(直到他的头发都变白了他才做到这件事,但他成功地实现了他小时候对自己许下的不可能的誓言。)可知,这篇文章的主题是决心能创造奇迹。故选C。