It's the Immune system!
good luck
It is extremely useful for geologists, because most specimens of a given mineral are very close to the same hardness. ... So, we can conclude that not all the rocks are hard, and the hardness of rocks depends on how the atoms of the rock's minerals are bound to each other and how they are arranged.
False !! covallent bond is formed by sharing ; iconic bond is formed by donation or transferring electrons !!
I would say that B) single events or several causes working together to produce extinction in a short period is referred to as mass extinction, but I am not 100% sure.