I can't tell if they are fertile

[Ominous cock]

Dear community,
I am not so experienced in telling if an egg is fertile or not. Would you please help me?
In some eggs I see a kind of doughnut, but Im not sure if it is as marked as it should be for a fertile egg.
Please tell me what do you think for these 3 eggs:

 

[MattCopeland]

All are fertile