Up to now no one has come up with a（n）explanation of why dinosaurs died out and it remai

问题补充：

Up to now, no one has come up with a（n）explanation of why dinosaurs died out, and it remains a mystery．

A. astonishing

B. amusing

C. convincing

D. puzzling

答案：

A. astonishing

B. amusing

(答案→)C. convincing

D. puzzling

解析：A．astonishing 令人惊讶的，B．amusing令人发笑的，C．convincing令人信服的，D．puzzling令人困惑的，句意：直到现在，没有人给出一个令人信服的解释为什么恐龙会灭绝，这仍然是和迷。所以选C。