The correct option is A 3-methyl-trans-3-octene.
The given hydrocarbon has eight carbon atoms in its parent chain which would be alkene because of presence of double bond between third and fourth position. If we start numbering the chain from left hand side so that the substitute comes closer to first carbon then the methyl group comes on third position (and it is in trans position compared to ethyl group). Hence, the name 3-methyl-trans-3-octene.