Adenine, guanine, cytosine, and thymine are the four nitrogenous bases present in the dna of all organisms. which scientist discovered these bases?

Erwin Chargaff  discovered the nitrogenous bases

Explanation:

Erwin Chargaff  discovered the nitrogenous bases present in the dna of all organisms. He conducted studies to reveal the structure of DNA and its primary chemical composition. In the initial stage of his experiment,  he noted that though the composition of nucleotide varies in all organism, there are certain properties which are same in DNA of all organism. This led chargaff to find the nucleotide bases with their pairing rule where  Adenine (A) binds with Thymine (T) and Cytosine (C) binds with Guanine (G).

the correct answer is option b

behavioral response need communication and thus co-ordination at several levels such as interaction among cells, organ system and the entire organism.

behavioral response produces both internal and environmental stimulus.