I think maybe the nephrons ...but not sure...
        
             
        
        
        
Answer:
a) R= allele for red colored flower
I= Allele for ivory flowers
b) Genotype of pink flowered plant: RI
c) Incomplete dominance
d) 100%
Explanation:
When the dominant allele is not able to fully mask the expression of the recessive allele in the heterozygous state, it is said to be incomplete dominance. The R and I alleles impart red and ivory color respectively to the flowers of the snapdragon plant. The heterozygous genotype "RI" imparts a pink color to the flowers and therefore, the alleles are said to exhibit incomplete dominance. 
The genotype of red-flowered snapdragon plant = RR. The genotype of ivory flowered snapdragon plant= II. When a red-flowered snapdragon plant is crossed with an ivory flowered snapdragon plant, the progeny is heterozygous in nature with the "RI" genotype. The phenotype of the progeny is "Pink flower" since the R allele is incompletely dominant over the allele I. 
 
        
             
        
        
        
Gravity
Plant roots always grow downward because specialized cells in root caps detect and respond to gravity. This is an example of a tropism. A tropism is a turning toward or away from a stimulus in the environment. Growing toward gravity is called geotropism.
        
             
        
        
        
<span>Evolution can best be summed up by statement D - change in a population through genetic variation over time. The other statements do not refer to evolutionary changes, as these are changes that occur slowly, rather than suddely or with speed.</span>