Which of the following compounds is the most stable?

A line$-$angle formula shows a ring with six vertices. There is a double bond between the first and the second $($clockwise$)$ vertices. A CH$3$ group is attached to the first vertex. A CH$2$CH$3$ group is attached to the second $($clockwise$)$ vertex. A CH$3$ group is attached to the fifth vertex.

A line$-$angle formula shows a ring with six vertices. There is a double bond between the first and the second $($clockwise$)$ vertices. A CH$3$ group is attached to the second vertex. A CH$2$CH$3$ group is attached to the third vertex. A CH$3$ group is attached to the sixth vertex.

A line$-$angle formula shows a ring with six vertices. There is a double bond between the first and the second $($clockwise$)$ vertices. A CH$3$ group is attached to the third and the fifth vertices. A CH$2$CH$3$ group is attached to the sixth vertex.