托福听力official11 According to paragraph 3, when do caged starlings become restless? 答案解析

以restless定位到做第一句：Early in his research, Kramer found that caged migratory birds became very restless at about the time they would normally have begun migration in the wild.这句话中明确说了在他们要开始迁徙的时候变得restless，和C选项对应。注意此题容易误选A，很多同学读到了第三句中的restless。但原文说overcast的时候鸟的migratory orientation就没方向，跟restless无关。B跟A在同一句，都与问题无关，所以错；D在第四句，也跟问题无关，不选。