A hydrocarbon X adds on one mole of hydrogen to give another hydrocarbon and decolourises bromine water. X reacts with `KMnO_4` in presence of acid to give two moles of the same carboxylic acid. The structure of Xis
A. `CH_2=CH-CH_2CH_2CH_3`
B. `CH_3CH_2CH_2-CH=CHCH_3`
C. `CH_3CH_2CH=CHCH_2CH_3`
D. `CH_3CH=CHCH_2CH_2CH_3`