Answer:
D. 3:1
Explanation:
Gregor Mendel, in one of his numerous studies, performed a cross between purebred dominant (TT) pea plants and purebred recessive (tt) pea plants. All the offsprings of this cross appeared heterozygous tall (Tt) in the F1 generation. 
However, when he self-crossed the F1 generation i.e. Tt × Tt, Mendel obtained a phenotypic ratio of 3 tall plants (dominant traits) : 1 short plant (recessive). This showed that the masked gene (recessive) was still present. 
 
        
             
        
        
        
Yur answer would be A.exponential growth
hope it helped
        
             
        
        
        
C. Vegetation 
because even though cows are important, all life is and not just that species and then cars and factories are unnatural and would not be critical for the carbon cycle in nature.
        
             
        
        
        
Answer:
Please mark me brainliest
Explanation:
Many of these diseases can be prevented by the use of viral vaccines, which stimulate protective immunity against the virus without causing major disease. Viral vaccines may also be used in active viral infections, boosting the ability of the immune system to control or destroy the virus.