"What aspect of American democracy first emerged because of disparities in size between the colonies that became the United States?"

The correct answer to this open question is the following.

Although you did not include options, we can say the following.

The aspect of American democracy that first emerged because of disparities in size between the colonies that became the United States was the Connecticut Compromise.

We are talking about the difficult moment in the Constitutional Convention of 1787 in Philadelphia, Pennsylvania. Federalists and Antifederalists were discussing their own postures, delegates from the colonies tried to defend their interests, and some plans such as the Virginia Plan and the New Jersey Plan confronted the delegates.

After so much discussion, the Connecticut Compromise, also known as the Great Compromise of 1787 was the agreement between small states and large states that established the representation in Congress.