Answer:
Listen to pronunciation. (al-VEE-oh-ly) Tiny air sacs at the end of the bronchioles (tiny branches of air tubes in the lungs). The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out.
 
        
                    
             
        
        
        
Answer:
Option-D, a segment of DNA
Explanation:
A gene represents the particular segment of DNA which contains the instruction for the trait of an organism. The nucleotide sequence present in the segment provides the instruction in the form of codons.
The gene is present in the form of its alternative form called alleles which are located on the chromosomes at locus. The alleles represent the variants of the gene and therefore controls the two variety of a single trait.
Thus, Option-D is correct.
 
        
             
        
        
        
This reaction occurs in the thylakoids of the chloroplast