Final answer:
All the given statements are correct regarding bases in human DNA, reflecting Chargaff's rules of base-pairing where %A equals %T, %G equals %C, and purines equal pyrimidines.
Step-by-step explanation:
The correct description regarding bases in human DNA is that %A is equal to %T, and %G is equal to %C. Additionally, the percentage of purines (A + G) is equal to the percentage of pyrimidines (T + C).
This is due to the base-pairing rules discovered by Erwin Chargaff, where adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). As a result, in DNA, the number of adenine units is approximately equal to the number of thymine units, and the number of guanine units is approximately equal to the number of cytosine units, forming complementary base pairs.