The correct answer is C. barricades.
A barricade is a temporary structure, often made of overturned vehicles, furniture, or other objects, that is used to block a road or other passage. Barricades are often used to prevent access to a building or area, or to slow down or stop the movement of people or vehicles.
Dykes are artificial embankments or walls that are built to prevent flooding. Barrages are barriers that are built to control the flow of water, such as in a river or canal. Barracks are buildings where soldiers live.
In the context of the question, the authorities erected barricades to block off the streets in anticipation of renewed rioting. This would prevent people from entering or leaving the area, and would also make it more difficult for rioters to move around.