31. Which is the IUPAC name for the following cycloalkane? (A) 2,4-dimethyl-1-ethylcyclopentane(B) 1,3-dimethyl-5-ethylcyclopentane (C) 1-ethyl-2,4-dimethylcyclopentane(D) 1-ethyl-3,5-dimethylcyclopentane