Z is a gaseous hydrocarbon with a density of $3.50 \times 10^{-3}\,\text{g cm}^{-3}$ at room conditions. When Z is treated with an excess of hot concentrated acidified $\text{KMnO}_4$, the reaction produces only one kind of carboxylic acid. What is Z?
- Abut-2-ene
- B2,3-dimethylbut-2-ene
- Chex-2-ene
- Dhex-3-ene