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:
What is sometimes combined with an RPG tube to keep from harming the user?, Context: Rocket-propelled grenades can be—and often are—used against hovering helicopters (e.g., by Somali militiamen during the Battle of Mogadishu (1993)). Firing an RPG at steep angles poses a danger to the user, because the backblast from firing reflects off the ground. In Somalia, militia members sometimes welded a steel plate in the exhaust end of an RPG's tube to deflect pressure away from the shooter when shooting up at US helicopters. RPGs are used in this role only when more effective weapons are not available.

Ex Output:
a steel plate in the exhaust end


Ex Input:
Who found that physical action cannot take on an arbitrary value?, Context: Classical statistical mechanics requires the existence of h (but does not define its value). Eventually, following upon Planck's discovery, it was recognized that physical action cannot take on an arbitrary value. Instead, it must be some multiple of a very small quantity, the "quantum of action", now called the Planck constant. Classical physics cannot explain this fact. In many cases, such as for monochromatic light or for atoms, this quantum of action also implies that only certain energy levels are allowed, and values in between are forbidden.

Ex Output:
Planck


Ex Input:
What happened on the Harlem River that helped people's anger?, Context: The development of the Bronx is directly connected to its strategic location between New England and New York (Manhattan). Control over the bridges across the Harlem River plagued the period of British colonial rule. Kingsbridge, built in 1693 where Broadway reached the Spuyten Duyvil Creek, was a possession of Frederick Philipse, lord of Philipse Manor. The tolls were resented by local farmers on both sides of the creek. In 1759, the farmers led by Jacobus Dyckman and Benjamin Palmer built a "free bridge" across the Harlem River which led to the abandonment of tolls altogether.

Ex Output:
a "free bridge"