Which of the following can not act as both oxidising and reducing agent ?

Options

A. `H_2SO_3`
B. `HNO_2`
C. `H_3PO_4`
D. `H_2O_2`

Explanation

To determine which of the following compounds cannot act as both an oxidizing and reducing agent, we need to analyze each compound's oxidation states and their ability to undergo oxidation and reduction.

**Step 1: Understand the definitions**
- An **oxidizing agent** is a substance that gains electrons (is reduced) and causes another substance to be oxidized.
- A **reducing agent** is a substance that loses electrons (is oxidized) and causes another substance to be reduced.

**Step 2: Analyze each compound**

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