The statement "It has three branches of government" is true about the government of Puerto Rico. Puerto Rico has an executive branch, a legislative branch, and a judicial branch, similar to the structure of the U.S. federal government.
The statement "It does not have its own constitution" is false; Puerto Rico has its own constitution, enacted in 1952.
The statement "The president of the United States has no authority over Puerto Rico" is also false; while Puerto Rico has a degree of self-governance, the U.S. Congress has the power to legislate for Puerto Rico, and the president, as part of the federal government, has some authority.
So, the correct response is: It has three branches of government.