What is the reason behind the difference in stability of the given alkenes?

Cyclohexa-1,3-diene is more stable because it has conjugated double bonds.

Cyclohexa-1,3-diene is more stable because it has unconjugated double bonds.

Cyclohexa-1,3-diene is more stable because it has more substituted double bonds.

Cyclohexa-1,3-diene is more stable because it has less ring strain.