You didn't place any of your following answers, which makes it difficult for people to help. What do you think it is? Out of the options that you have.
The challenges range from terrorism and violent extremism, to piracy, political instability, elections-related violence, drug trafficking or deadly viruses.
Atoms usually engage in chemical reactions which will end in complete outer electron shells. Most of the time, a complete outer shell usually means 8 electrons, except for a couple light elements which only require 2 electrons to have a whole outer shell.
In the late Mesozoic era, the region was affected by a series of orogenies that deformed western North America and caused a great deal of uplift. Eruptions from volcanic mountain ranges to the west buried vast regions beneath ashy debris. <span />
