• Stoichiometric Oxygen Requirement for Methane Combustion:
• Stoichiometric Reaction Equation:

$$\text{CH}_4 + 2\text{O}_2 \longrightarrow \text{CO}_2 + 2\text{H}_2\text{O}$$

• Molecular Weights:
• $\text{CH}_4 = 12 + 4(1) = 16\text{ g/mol}$
• $2\text{O}_2 = 2 \times (2 \times 16) = 64\text{ g/mol}$
• Mass Ratio:

$$\text{Mass of Oxygen required per kg of Methane} = \frac{64\text{ kg }\text{O}_2}{16\text{ kg }\text{CH}_4} = 4\text{ kg }\text{O}_2$$

• Conclusion: Four kilograms of oxygen are required (Option 4).

Correct option: (4) Four