The correct option is A ROH+SOCl2⟶
Find the reaction from given choices in which product are gaseous and hence, easy to remove.
ROH+SOCl2⟶RCl+SO2↑+HCl↑
∵SO2 and HCl are gaseous by-products and can be removed easily to get pure alkyl halide.
∴ It is the best method for preparation of alkyl halides