Final answer:
The power of a parliamentary democracy is justified through the principle of popular sovereignty, where citizens have the authority to elect representatives who choose the executive leadership. Parliamentary democracies often have checks and balances to hold the executive accountable.
Step-by-step explanation:
In a parliamentary democracy, the power of the government is justified through the principle of popular sovereignty. This means that the citizens have the ultimate authority to choose their representatives in the legislative branch, who in turn choose the executive leadership from among themselves.
By giving citizens the power to elect their representatives, parliamentary democracies ensure that the government derives its power from the people. Additionally, parliamentary democracies often have checks and balances in place, such as a vote of no confidence, to hold the executive accountable to the legislative branch and ensure transparency and accountability.