In this task, you're given a passage, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both passage and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the passage or linked information.

Passage: Walsh first developed what would become the West Coast offense when he was offensive coordinator of the Cincinnati Bengals, working under legendary head coach Paul Brown. However, Walsh truly perfected this strategy as the head coach of the San Francisco 49ers. His teams were led by quarterback Joe Montana. Montana, who was noted for his ability to remain calm under pressure, also possessed good mobility and an accurate passing arm. Another important player in the 49ers offense was Roger Craig, a swift, speedy running back who could also catch passes out of the backfield and was a good receiver. Walsh's 49ers teams also featured several All-Pro wide receivers, including Dwight Clark, John Taylor, and Jerry Rice. The 49ers were one of the NFL's powerhouses in the 1980s and 1990s, under the guidance of head coaches Bill Walsh (1979–1988) and George Seifert (1989–1996). Walsh won three Super Bowls in the 1981, 1984 and 1988 seasons. Seifert won two Super Bowls in 1989 and 1994. Montana, Walsh and Rice are in the Pro Football Hall of Fame, and so is Montana's successor, quarterback Steve Young. Like Montana, Young was a great running quarterback and a very efficient passer. 
 Link Information: In the spring of 1993, at Montana's request, San Francisco traded Montana to the Kansas City Chiefs. Young was now the 49ers' undisputed starter, Answer: 1993
What year did Montana's successor take over?

Passage: Belgrade marshalling yard () or Makiš railway station (), or Makiš freight station, is a classification yard of the Belgrade railway junction and the largest railway station in Serbia. It is located in the neighbourhood of Makiš in Čukarica of Belgrade. The railroad continues to Ostružnica in one line via park A, in the other direction to Ostružnica via park B, in third direction to Resnik via junction B near Železnik and junction K of Belgrade railway junction near Petlovo Brdo, in fourth direction to Resnik via junction R in the tunnel below Vidikovac and junction A near Kneževac, in the fifth direction to Rakovica via park B and junction R, in the sixth direction to Rakovica via park A and junction T, in the seventh direction to Rakovica via park B and junction T per second line and the eight towards direction to Jajinci. Belgrade marshalling yard consists of 120 railway tracks.
 Link Information: The urban area of Belgrade has a population of 1.23 million, while nearly 1.7 million people live within the administrative limits of the City of Belgrade  Answer: 1.23 million
How many people live in the city that the largest railway station in Serbia is located in?

Passage: Indigenous peoples inhabited Missouri for thousands of years before European exploration and settlement. Archaeological excavations along the rivers have shown continuous habitation for more than 7,000 years. Beginning before 1000 CE, there arose the complex Mississippian culture, whose people created regional political centers at present-day St. Louis and across the Mississippi River at Cahokia, near present-day Collinsville, Illinois. Their large cities included thousands of individual residences, but they are known for their surviving massive earthwork mounds, built for religious, political and social reasons, in platform, ridgetop and conical shapes. Cahokia was the center of a regional trading network that reached from the Great Lakes to the Gulf of Mexico. The civilization declined by 1400 CE, and most descendants left the area long before the arrival of Europeans. St. Louis was at one time known as Mound City by the European Americans, because of the numerous surviving prehistoric mounds, since lost to urban development. The Mississippian culture left mounds throughout the middle Mississippi and Ohio river valleys, extending into the southeast as well as the upper river.
 Link Information:  earthworks are artificial changes in land level, typically made from piles of artificially placed or sculpted rocks and soil. Answer:  sculpted rocks and soil.

What are earthwork mounds made of?