The pax romana ended in 180 ce after over one hundred fifty years in existence. the end of this era ushered in a period of
a. inflation.
b. foreign wars.
c. religious wars.
d. political instability.

D. political instability.

Explanation:

The Pax Romana is a period when there were peace and stability across the Roman Empire that lasted for over one hundred and fifty years. The end of this era ushered in a period of great instability, where there were civil wars leading to the division of the empire, political conspiracies leading to in many senators been assassinated and provincial and slave rebellions.  

answer: secession

secession, as it applies to the outbreak of the american civil war, comprises the series of events that began on december 20, 1860, and extended through june 8 of the next year when eleven states in the lower and upper south severed their ties with the union. the first seven seceding states of the lower south set up a provisional government at montgomery, alabama. after hostilities began at fort sumter in charleston harbor on april 12, 1861, the border states of virginia, arkansas, tennessee, and north carolina joined the new government, which then moved its capital to richmond, virginia. the union was thus divided approximately on geographic lines. twenty-one northern and border states retained the style and title of the united states, while the eleven slave states adopted the nomenclature of the confederate states of america.

explanation:

he sent troops to protect the students as they entered the school.