The government designed at the constitutional convention allowed the voters to directly elect select one: a. the president and all members of congress b. only the senate c. only the house of representatives d. only the president

c. only the house of representatives

This was part of the efforts of the Convention to create a federal government since it  had, by that time, become clear that the Articles of Confederation were not a good enough constitution for the new nation.

d.summerains, the last one

the answer is a. laws were enacted in the aftermath of the plot to make it harder to free slaves,increasing sectionalism