Hint: Dockyards at the Indus valley site were the huge tanks where ships and boats used to come in from the sea through canals. Goods were probably loaded and unloaded here. The city where the dockyard was found stood beside a tributary of Sabarmati in Gujarat.
Complete answer: The dockyard at Indus valley civilization was found in lothal. Apart from the dockyard, the city had raw materials such as semi-precious stones etcetera. It was also an important centre for making objects out of stone metal and shells. Now we will discuss why the other three are not the correct answers.
-The Ropar area of the ancient Indus valley civilization is situated on followed through the Sutlej onto Himachal Pradesh state. The place was famous for agricultural products and small weaving and iron products industries.
-Kalibangan was famous for fire altars where sacrifices may have been performed.
-Banawali of Indus valley civilization had houses with rammed earth and floors. The houses were planned with rooms and toilets and constructed on either side of streets and lanes. The site has major archaeology importance.
Therefore the correct answer is option-A.
Note: It also had a storehouse and many ceilings and seals with impressions on clay were found in the storehouses. The storehouse found in Lothal was probably a workshop for making various things like beads, half made beads, pieces of stones tools for making beads and finished beads have been found here.