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参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】Year after year a dedicated Swedish chemist worked to find a substance which, when (1)_____ nitroglycerine(硝化甘油), would make explosives safer to handle (2)_____ weakening their force. He had a persona...
A.
mixing with
B.
mixed with
C.
was mixing with
D.
was mixed with