The reason why haplotype blocks are still useful on current populations is because
a) some of our human ancestors interbred with neanderthals.
b) new mutations cannot be introduced into existing haplotype blocks.
c) they are still preserved in their original ancient configurations.
d) disease genes are found in haplotype blocks.
e) modern humans descended from a relatively small population of about 10,000 individuals that existed about two thousand generations ago.

D) disease genes are found in haplotype blocks.

Explanation:

Given the high allelic variability in the human genome, the probability that two unrelated individuals have the same haplotype is virtually none. This is why the study of haplotypes has become a useful tool in the determination of the genetic relationship between individuals, and therefore in the study of the origin of mutations causing various diseases.

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.