The study of the end-Permian mass extinction is hindered by all of the following EXCEPT __

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The study of the end-Permian mass extinction is hindered by all of the following EXCEPT ______.

A.the lack of experienced researchers

B.lack of access to southern China

C.lack of relevant rock samples

D.lack of well-preserved fossils

请帮忙给出正确答案和分析,谢谢!

热搜:人体安全电流值是工频交流()mA、直流50mA