In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Ex Input:
The expansion of what further cemented Houston's emergence as a powerhouse commercial city?, Context: By 1860, Houston had emerged as a commercial and railroad hub for the export of cotton. Railroad spurs from the Texas inland converged in Houston, where they met rail lines to the ports of Galveston and Beaumont. During the American Civil War, Houston served as a headquarters for General John Bankhead Magruder, who used the city as an organization point for the Battle of Galveston. After the Civil War, Houston businessmen initiated efforts to widen the city's extensive system of bayous so the city could accept more commerce between downtown and the nearby port of Galveston. By 1890, Houston was the railroad center of Texas.

Ex Output:
bayous

Ex Input:
Storms have lots of?, Context: The Scooter is another storm, a white cloud group farther south than the Great Dark Spot. This nickname first arose during the months leading up to the Voyager 2 encounter in 1989, when they were observed moving at speeds faster than the Great Dark Spot (and images acquired later would subsequently reveal the presence of clouds moving even faster than those that had initially been detected by Voyager 2). The Small Dark Spot is a southern cyclonic storm, the second-most-intense storm observed during the 1989 encounter. It was initially completely dark, but as Voyager 2 approached the planet, a bright core developed and can be seen in most of the highest-resolution images.

Ex Output:
clouds

Ex Input:
What caused Northern Rocks downfall?, Context: Initially the companies affected were those directly involved in home construction and mortgage lending such as Northern Rock and Countrywide Financial, as they could no longer obtain financing through the credit markets. Over 100 mortgage lenders went bankrupt during 2007 and 2008. Concerns that investment bank Bear Stearns would collapse in March 2008 resulted in its fire-sale to JP Morgan Chase. The financial institution crisis hit its peak in September and October 2008. Several major institutions either failed, were acquired under duress, or were subject to government takeover. These included Lehman Brothers, Merrill Lynch, Fannie Mae, Freddie Mac, Washington Mutual, Wachovia, Citigroup, and AIG. On Oct. 6, 2008, three weeks after Lehman Brothers filed the largest bankruptcy in U.S. history, Lehman's former CEO found himself before Representative Henry A. Waxman, the California Democrat who chaired the House Committee on Oversight and Government Reform. Fuld said he was a victim of the collapse, blaming a "crisis of confidence" in the markets for dooming his firm.

Ex Output:
home construction and mortgage lending