A. To investigate the learning abilities of a type of migratory bird
B. To address a possible cause of population decline in a bird species
C. To explain puzzling data from an earlier research study
D. To confirm a long-standing hypothesis about an animal behavior
我的笔记 编辑笔记
原文定位：
What was so special about that day? And why did the pigeons released at jersey hill disappear every other time? For years, no one had an answer. But in 2015, a scientist named Jonathan Hagstrum looked at the previous data and did a new study.
选项分析：考察转折考点，材料提到在之前的研究中，有一部分的信鸽不能回到放飞地Jersey Hill，无人能知道原因，但接下来乔纳森·哈格斯特鲁姆要重新研究这个问题，可知要选择C选项。ABD选项均未提及。
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