Generally speaking, "d.Language barriers" were not a problem faced by multi-ethnic countries in Africa after independence, since relative to some of the more serious problems, like genocidal violence, this was not an issue.
Implementing an executive order.
Executive orders are orders issued by the President to the executive branch that carry the force of law. That is, the branches are required to implement the actions of the President's executive order.
The answer is ice storms. According to wiki
The Louisiana Purchase eventually doubled the size of the United States, greatly strengthened the country materially and strategically, provided a powerful impetus to westward expansion.
The answer should be D, Doubled the size of the country
