Answer:
D. all government leaders ultimately answer to the power of ordinary citizens
Explanation:
A bill becomes law if signed by the President or if not signed within 10 days and Congress is in session. If Congress adjourns before the 10 days and the President has not signed the bill then it does not become law ("Pocket Veto.")
The Sahel was the last area in the northern parts of Africa, where vegetation can survive and where people were living at the time. Following the Sahel to the North one can find the Sahara desert which is a natural barrier that no invading force could trespass.