5. In the following reaction, 2H₂O₂(l) → 2H₂O(l) + O_2(g) , hydrogen peroxide functions as
1. an oxidizing agent.
2. a reducing agent.
3. an acid.
(A) 1 only
(B) 2 only
(C) 3 only
(D) 1 and 2 only

此反應為H2O2的自身氧化還原反應，因此...