Sometimes biologists are alleged to have said that "man comes from monkeys." the correct way for a modern biologist to explain the apparent sequence of human evolution is:

humans and monkeys share a common ancestor.

Explanation:

Modern humans, the Homo sapiens species, did not evolve from monkeys, but share a common ancestor with them.

"A very common mistake is to think that 'we descend from monkeys'. That mistake causes many people to deny the theory of evolution"

"To begin, it is better to affirm that we are one more species of the order primates"

This lineage of primates "begins its evolutionary history about 7 million years ago. At that time, a common ancestor with chimpanzees diverged in two different lineages, probably due to climatic reasons."

"The lineage that gave rise to chimpanzees, Pan paniscus and Pan troglodytes, remained in West Africa. The lineage that ultimately gave rise to today's humanity evolved in southern and eastern Africa."

Evolution is a process that can be very slow and some of its vestiges may remain long after they stop fulfilling a function. An example is the appendix, which would have fulfilled in our ancestors a function related to the digestion of cellulose from plants.

The history of our origins is constantly changing as new fossils are discovered.  "Our species, Homo sapiens, emerged in Africa just over 200,000 years ago. Some researchers think that certain fossils from a site in Morocco (Jebel Irhoud) already belonged to our species. Those fossils are 315,000 years old."

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

the answer to your question is:

c. complementary base-pairing