2. Which of the following correctly ranks the cycloalkanes in order of increasing ring strain per methylene? (A) cyclopropane < cyclobutane < cyclohexane < cycloheptane (B) cyclohexane < cyclopentane < cyclobutane < cyclopropane (C) cyclopentane < cyclobutane < cyclohexane < cyclopropane (D) cyclopentane < cyclopropane < cyclobutane < cyclohexane (E) cyclopropane < cyclopentane < cyclobutane < cyclohexane