The sun
is beacuse ti is the biggest star ever
We need to know the dominant and recessive traits of the noombats in order to answer this question. If both of them has yellow as the dominant trait, then green may be recessive. In that case there is a chance for them to have a green bellied child. Its impossible to tell the percentage though because we don't know enough about the animals.
People, coal, and gasoline are sources of CO2
More growth of flowers and or more plant food/water supply for it
I believe the answer is a. crossing over
