Which of the following has two equatorial alkyl substituents in its most stable conformation? () A: 1,1-dimethylcyclohexane B: cis-1,2-dimethylcyclohexane C: cis-1,3-diethylcyclohexane D: cis-1,4-diethylcyclohexane E: trans-1,3-diethylcyclohexane