There are three different substances with the formula C₄H₈ that do not contain a ring. What are they? a) Butene, Isobutene, 1,2-Butadiene b) Butane, 2-Methylpropene, Cyclobutane c) Ethylene, Propylene, Butadiene d) 1-Butyne, 2-Butyne, 1,3-Butadiyne