Chemical changes in the structure shown are most likely to happen during a) exposure to water. b) exposure to high humidity. c) exposure to mutagenic agents. d) exposure to high oxygen levels.

Option C

Explanation:

Mutagenic exposure can causes changes in the structure of the DNA. These changes are primarily chemical changes which can causes absurd mutations which can be harmful as well.  

For example - cancer is caused due to mutagenic change in DNA.  

Exposure of radioactive substance such as x-rays, ultraviolet radiation and radioactive chemicals such as uranium causes mutation in the genes.  

Hence, option C is correct

this is math not biology xd