The compound that can act both as oxidising and reducing agent is:

Options

A. `KO_(2)`
B. `Mn_(2)O_(7)`
C. `Al_(2)O_(3)`
D. `SO_(3)`

Explanation

To determine which compound can act both as an oxidizing agent and a reducing agent, we need to analyze the oxidation states of the given compounds.

### Step-by-Step Solution:

1. **Understanding Oxidizing and Reducing Agents**:
- 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.

2. **Identifying the Compounds**:
- The compounds in the question are:
1. SO3 (sulfur trioxide)
2. Al2O3 (aluminum oxide)
3. Mn2O7 (manganese heptoxide)
4. KO2 (potassium superoxide)

3. **Analyzing SO3**:
- In SO3, sulfur has an oxidation state of +6. Since it is in its maximum oxidation state, it cannot act as a reducing agent. Thus, it can only act as an oxidizing agent.

4. **Analyzing Al2O3**:
- In Al2O3, aluminum has an oxidation state of +3. Similar to SO3, it is also in a high oxidation state and cannot act as a reducing agent.

5. **Analyzing Mn2O7**:
- In Mn2O7, manganese has an oxidation state of +7. Again, being in its maximum oxidation state, it cannot act as a reducing agent.

6. **Analyzing KO2**:
- In KO2 (potassium superoxide), the oxidation state of the superoxide ion (O2^-) is -1. This means it can lose an electron to become O2 (oxidation) or gain an electron to become O2^2- (reduction). Therefore, KO2 can act both as an oxidizing agent and a reducing agent.

7. **Conclusion**:
- Among the given options, KO2 is the only compound that can act both as an oxidizing agent and a reducing agent.

### Final Answer:
The compound that can act both as an oxidizing and reducing agent is **KO2** (potassium superoxide).

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