OG3 阅读 Q22

Choice A is the best answer. In (lines 6-9"wings...project"), the author explains that Dial was "challenged," or dared, by graduate students to develop "new data" on a long-standing scientific debate (the "ground-up-tree-down" theory).
Choices B, C, and D are incorrect because in this context "challenged" does not mean required, disputed with, or competed with.