题目

At the concert the singers will ________ everyone to protect the environment.    A．call up                      B．call for    C．call off                     D．call on 答案：D　考查短语辨析。call up打电话；call for要求，提倡，为……叫喊；call off取消；call on号召，呼吁，正式邀请。句意：在音乐会上，歌手们将号召大家保护环境。故答案应为D项。

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