Answer: B
The stable chair has Br and CHX3 both equatorial. E2 needs the diaxial conformer, where CHX3 on C2 is axial, so the C2-H is equatorial and not anti to Br. Only the axial H on C6 is anti-periplanar, giving the double bond C1=C6, i.e. 3-methylcyclohexene, despite its lower substitution.