Concept: Popular sovereignty means ultimate power rests with the people.
Explanation: Citizens exercise sovereignty by taking part in the democratic process.
The most formal and direct way is voting at elections to choose representatives.
Through voting, citizens give the government its authority and consent.
Attending rallies or registering to vote are supporting activities but do not themselves transfer power.
Suing the state is a legal right, not the exercise of sovereign authority.
Therefore, the exercise of popular sovereignty is seen in the act of voting.
Answer: B. voting at elections