A blend of $10\ \text{cm}^3$ of methane and $10\ \text{cm}^3$ of ethane was ignited with an excess of oxygen. Once it had cooled to room temperature, the remaining gas was then led through aqueous potassium hydroxide. Every gas volume was measured at the same temperature and pressure. What volume of gas did the alkali absorb?
- A$15\ \text{cm}^3$
- B$20\ \text{cm}^3$
- C$30\ \text{cm}^3$
- D$40\ \text{cm}^3$