Which of these reactions are redox reactions? Check all that apply.

A, D, and E are redox reactions because oxidation states change in each. In A, Cd goes from 0 to +2 while hydrogen goes from +1 to 0. In D, sulfur changes from −2 to +4 and oxygen from 0 to −2; in E, carbon changes from −4 to +4 and oxygen from 0 to −2. In B and C, the elements keep the same oxidation states, so those reactions are not redox.

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