Water makes up 90% of the body.
On the off chance that a change happens, if beneficial in the scarcest, normal choice picks it to wind up noticeably the more typical quality, and consequently development happens. For instance the dark demise wiped out one in three Europeans, now researchers are finding that some of the individuals who survived had transformations on their resistant framework cells; they needed regular receptors, or generally had few. (DNA resembles history, obviously, they aren't meeting with dark torment patients, the DNA in Caucasian Europeans goes about as an authentic guide of past bottlenecks.) Because Europeans with this transformation were to the least extent liable to bite the dust of the dark passing they were the well on the way to survive, which is the reason the calamity of the bubonic torment brought about somewhere in the range of 20% of Caucasian European relatives to do not have these receptors on their invulnerable framework cells which thusly diminishes the danger of resistance illnesses, for example, assistants.
egg (female) and sperm ( male)
To part A the answer is continental drift :D to Part B the answer is Mid-ocean ridges :D Hope I was helpful
