Answer:
A. Nationalist revolutionaries embraced the concept of popular sovereignty to call for an end to absolute monarchies.
Step-by-step explanation:
During the peak era of nationalism, most countries in the world adopted a monarchy system. This system gave a single king as the absolute ruler who can do anything within the government body. Sometimes, these kings do this at the expense of the people.
Revolutionaries realized how corrupt this system is.
They adopted the idea from the enlighten thinkers who promoted a concept of government that enable the people to influence the government. This concept is called popular sovereignty. They forcefully remove the nobles from their power and establish democracy as a new system of government.