<span>There are three major groups of mammals, categorized on the basis of their method of reproduction. Monotremes lay eggs to have children instead of having the mother bear them. The second type of mammal is the marsupial, which are non-placental animals who carry their young in their pouches. Eutherians are the third group who are placental mammals.</span>
It always starts with evaporation, because without water vapor (the byproduct of evaporation), there would be no clouds (they are made out of water vapor and some other particles). Henceforth, there will be no rain.
Double-stranded RNA is the answer to this question that you have asked
I believe the answer is a mutation.