А what is a highly tested, generally accepted principle
that explains a vast number of observations and experimental data.*

i believe it would cause an increase of percipitation, though i could be wrong. so i would say b is the answer.

an organism's phenotype is the  form of a trait  that it  displays. for  flowercolor, a pea  plant  can  display  a phenotype of purple or white flowers. an organism's  genotype  is the alleles of a gene it contains. based on his data, mendel concluded that a phenotype can be  determined  by more than one  genotype.

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.