题目

     Have you seen Jurassic Park? In this film, scientists use DNA kept for tens of millions of years to clone dinosaurs. They find trouble, however, when they realize that the cloned creatures are smarter and more dangerous than expected. That’s nothing more than a fiction.      But could we really clone endangered animals?      To date, the most successful attempt to do so was the cloning of a gaur, a rare ox-like animal from southeast Asia. Scientists used a cow to bring the cloned baby gaur, named Noah. Two days after birth, however, Noah died from a common bacterial infecti科学研究表明，对幼鼠注射或口服睾丸酮后，出生仅14天的雄鼠就表现出交配行为。如果将公鸡的睾丸摘除，公鸡将不再啼鸣，鸡冠萎缩，求偶行为消失；重新植入睾丸，则公鸡的特征和交配行为又得以恢复。这些事实说明                  A．性激素与性行为之间有着直接的联系B．被割除睾丸的公鸡变成了母鸡，因而不再啼鸣C．睾丸酮属于雄激素，在雌性体内不存在D．幼鼠和公鸡的有关特征和行为变化是激素和神经系统共同作用的结果