What science was developed later which was found to support darwin's theory?

The best answer would most likely be genetics or genetic theory.

There were many doubts about Darwin's theory because Darwin could not yet describe the mechanism of inheritance. Mendel's work on inheritance was already published, 2 years earlier, but this eluded Darwin. It was only till after Darwin's death that the science of genetics came about.

This union brought about the "modern synthesis," a theory that proposes that both genetics and natural selection is a result of evolutionary changes.

the offspring would all be white. if the parents are both white flowers then they have the genotype rr, which when crossed results in an all white punnet square.

the correct answer is 2 and 4