Final answer:
The delegates at the Constitutional Convention of 1787 spent time debating the structure of the legislature in the proposed Constitution because they wanted to ensure a balanced and representative branch of government, avoid gridlock, and avoid the weaknesses of the Articles of Confederation.
Step-by-step explanation:
The delegates at the Constitutional Convention of 1787 spent a significant amount of time debating and refining the structure of the legislature in the proposed Constitution. This was a crucial issue for the delegates for multiple reasons. First, they believed that the legislature would be the most powerful branch of government and wanted to ensure it was balanced and representative. Second, they were concerned about the potential for gridlock and wanted to create a system that could effectively make laws. Third, they wanted to avoid the mistakes of the Articles of Confederation, which had a weak central government and a unicameral legislature. Therefore, the correct option is (d) All of the above.