25 percent if you make a punnet square for this it would help a lot. Homo is same and if its dominant it would be big letter like FF and homo recessive would be ff you would get FF,Ff,Ff,ff in the punnet square.
4. Petroleum.
Hope this helps!
Answer:
1/ Climate change
2/ Asteroid impacts
3/ Massive volcanic eruptions
4/ Sun explodes
etc. (all the things above are most likely to happen but alien invasion or things like that is also a theory that you can add depends mostly if you like it or not)