The correct answer is B) create a constitution.
According to this excerpt from the Tennis Court Oath, the National Assembly believed its job was to create a constitution.
In the conflictive years of the French Revolution, the Tennis Court Oath of 1789 was the oath that the Third State members took to not separated themselves until the goal of having a new constitution was accomplished. They took the oath on June 20, 1789. The idea was promoted by members of the National Assembly such as Comte de Mirabeau and Honore Gabriel Riqueti.