D．caused a rise in the number of sheep

　　解析：选A　推理判断题。根据第三段中的"People feared that the plant was gone forever."和"the people who ran the park took the sheep away from the area, hoping that the hawkweed might return"可知，当斯诺登水兰在1953年凭空消失后，人们对此很担心。

　　6．The underlined word "extinct" in Paragraph 3 probably means "________"．

　　A．growing B．disappearing

　　C．unusual D．dangerous

　　解析：选B　词义猜测题。根据第三段中的"the Snowdonia hawkweed disappeared. People feared that the plant was gone forever"可知，人们曾一度以为斯诺登水兰灭绝了。故画线词意为"消失了的；灭绝的"。

　　C

　　Robert Frost was born in San Francisco in 1874, but he spent most of his life moving from place to place, often returning to New England, the place of his later childhood and early adult years.

　　Robert was the first child born in his family. Frost's early childhood was filled with anxiety, since his father drank and gambled too much. Frost's father died when Frost was 11, leaving his mother with no choice but to move back home with her parents in Lawrence, Massachusetts.

　　Frost's first published poem appeared in the Lawrence High School Bulletin in 1890. While Frost could attend Harvard College, he attended Dartmouth College instead, because his grandparents thought he would find success there. Frost dropped out of Dartmouth before his first year was over and began teaching primary school.

　　In 1894, Frost received his first payment for the poem My Butterfly: an Elegy. He worked as a reporter while still teaching primary school. Frost married his wife, Elinor White, in 1895. Frost and Elinor had their first child in 1896, a son they named Elliot.

　　In 1897 Frost continued his education at Harvard College, but by 1899 he had dropped out again. In 1901, Frost's grandfather died, leaving him a farm in New Hampshire, which made it possible for Frost to support his growing family. Robert and Elinor had more children, and Frost wrote more and did several different part­time jobs to make ends meet. He taught English literature, trained other teachers in teaching methods, and taught education and psychology classes.

　　In 1913, his first book A Boy's Will was published. The success of this book brought him in contact with many important literary people, including William Yeats. Following this success, Frost published many literary works, including short stories, poems and a play. He made a living by lecturing, writing and sometimes teaching.

　　Frost actively contributed to the literature until his death in 1963. Frost was highly regarded, and he was awarded the Pulitzer Prize for his poetry four times in his life.

语篇解读：本文主要介绍美国大诗人罗伯特·弗罗斯特的生平故事。

　　7．Robert Frost attended Dartmouth College instead of Harvard College because ________.

A．he didn't show any interest in Harvard College