The right option is; C. They are controlled by more than one gene  
Traits such as skin color, human height and eye colour are known as polygenic traits. These traits have wide variation throughout the human population and are controlled by two or more genes. For example the human height is controlled by at least three genes with six alleles. The quantities of the genes are usually large but often have a little effect.
 
        
             
        
        
        
The correct answer is option B, 50%
Let us take the following case:
Genotype of heterozygous parent - (Aa)
Genotype of homozygous parent – (aa)
Allele I  - (Aa)
Allele II – (aa)
The cross between the two is shown below:
Aa  X aa
Aa, Aa, aa, aa
There are 50 % Aa, and 50 % aa allele.  
Thus, the allele I (Aa) is 50 %.  
 
        
             
        
        
        
Petroleum, and carbon. It's an organic thing and has the sources provided. 
 
        
             
        
        
        
Answer:
Habitat destruction and degradation, illegal shooting, and the contamination of its food source, largely as a consequence of DDT, decimated the eagle population.
 
 
        
             
        
        
        
Answer: The answer is natural selection 
Explanation:
Natural selection explains how certain desirable traits like;
- shape of the beaks of Darwin's finches: to help them feed more easily 
 - industrial melanism to raise a population of dark-coloured organisms to evolve from pre-existing light coloured ones in industrial areas where the surrondings are blackened with soot; 
are favored over LESS DESIRABLE TRAITS, resulting in organisms that are most suited/adapted to thrive in an environment, which is evolutionary change