已知∠AOB=3∠BOC,若∠BOC=30°,則∠AOC等于A.120°B.12

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    問題補(bǔ)充:?jiǎn)芜x題 已知∠AOB=3∠BOC,若∠BOC=30°,則∠AOC等于?
    A.120°
    B.120°或60°
    C.30°
    D.30°或90°
    答案:B