What does the phrase “莫名其妙(mòmíngqímiào)” refer to?

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Advanced Level 高级 (gāojí)
What does the phrase “莫名其妙”(mòmíngqímiào)refer to?
A. Baffling
B. Downhearted
C. Ecstatic
D. Smug and complacent

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