Answer: A (\(\text{CH}_4\), \(\text{CO}\), \(\text{CO}_2\)). Complete combustion needs \(\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}\), so 100 cm³ of methane would require 200 cm³ of oxygen. Only 150 cm³ is available, so combustion is incomplete.
With too little oxygen the products are a mixture of \(\text{CO}_2\), \(\text{CO}\) and some unburnt \(\text{CH}_4\), plus water. On cooling to room temperature the water condenses and is no longer a gas.
The remaining gases are \(\text{CH}_4\), \(\text{CO}\) and \(\text{CO}_2\), option A. B includes water (condensed out), C needs excess oxygen, and D wrongly lists hydrogen. Answer A.
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