Answer: B, C
Anti-periplanar elimination needs axial Br and an axial H on the neighbouring carbon. In the cis isomer, axial Br goes with equatorial CH3, leaving an axial H on C2, so 1-methylcyclohexene can form. In the trans isomer, axial Br requires axial CH3 (diaxial), so the C2-H is equatorial and only C6-H is anti, giving 3-methylcyclohexene. That reactive conformer is the less stable diaxial chair, so trans reacts more slowly, not faster.