Which is the correct pair of complementary nitrogenous bases in dna? . a ) adenine and thymine . b ) cytosine and thymine. c ) guanine and thymine.

A ) adenine and thymine

Explanation:

DNA has two types of nitrogenous bases: purines and pyrimidines. Adenine and guanine are purines while cytosine and thymine are pyrimidines.  

A purine always pairs with a pyrimidine. Hence, adenine in DNA pairs with thymine while guanine pairs with cytosine. This is done to maintain the constant width of the double helix throughout the length.  

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-lavira: )

b is the correct answer