which reagent is used for the following reaction?

Question. Which reagent will you use for the following reaction?
CH₃​CH₂​CH₂​CH_3​→CH₃​CH₂​CH₂​CH₂​Cl+CH₃​CH₂​CH(Cl)CH₃

​a)Cl₂/UV light
b)NaCl+H2SO4
c)Cl₂ gas in dark
d)Cl₂ gas in the presence of iron in dark

Answer: ​a)Cl₂/UV light