Final answer:
The percentage of thymine will approximately be 38%, as Chargaff's rules dictate that the amount of adenine is equal to the amount of thymine and the amount of guanine is equal to the amount of cytosine in DNA.
Step-by-step explanation:
If cytosine makes up 38% of the nucleotides in a sample of DNA, according to Chargaff's rules, which state that DNA is composed of base pairs where adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C), the percentage of thymine in the DNA sample will also be approximately 38%. This is because the amount of adenine is equal to the amount of thymine, just as the amount of guanine is equal to the amount of cytosine.
Therefore, the correct answer to the question of what percentage of the nucleotides in this sample will be thymine is d) 38%.
The same rule applies to any other DNA sample. For instance, if a particular species of DNA has 27% adenine, the percentage of thymine would also be 27%, and the percentage of cytosine would be equal to the percentage of guanine, not 54% as some might mistakenly sum those percentages.