What year did the constitutional convention take place?.

May 25, 1787

Explanation:

The Constitutional Convention took place  in Philadelphia  between May and September of 1787 to address the problems of the weak central government that existed under the Articles of Confederation. Some of the delegates  included George Washington, who was elected to preside, James Madison, Benjamin Franklin, James Wilson, John Rutledge, Charles Pinckney, Oliver Ellsworth, and Gouverneur Morris.

  b.

there are isolated pockets of farming, generally around rivers and oases, which are used for irrigation.