题目

   Rachel Carson (1907-1964) was a pioneer of the world’s environmental movement through her writing about the protection of the natural world. Her 1962 book Silent Spring made her well known by many people. It describes the harmful changes in the environment of using toxic（有害的）chemicals on farmland. Carson's career started as a biologist in the US Bureau of Fisheries. In 1951 she published her first book. The Sea Around Us, which became a bestseller. It made her rich enough to leave her job and devote her life to writing. She was s gifted writer. Her next two books were a一黑色家兔与白色家兔杂交（家兔的毛色由两对等位基因控制且独立遗传），F1均为黑色。F1雌雄个体进行交配得F2，F2的性状分离比为黑色:浅黄色:白色=12:3:1,F1测交后代的性状分离比是A.2:1:1 B.3:1 C.1:3 D.1:1