[ C/U ]   audio   plural A’s or As in Western songs, the sixth Observe in the size (= series of notes) that begins about the Take note C, or simply a list of notes determined by this Notice知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。没收到验证码？ 重新发送 需要帮助？请 �