Teacher:In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Teacher: Now, understand the problem? Solve this instance: Passage: Washington, D.C. is located in the mid-Atlantic region of the U.S. East Coast. Due to the District of Columbia retrocession, the city has a total area of 68.34 square miles (177.0 km2), of which 61.05 square miles (158.1 km2) is land and 7.29 square miles (18.9 km2) (10.67%) is water. The District is bordered by Montgomery County, Maryland to the northwest; Prince George's County, Maryland to the east; Arlington County, Virginia to the south; and Alexandria, Virginia to the west.
The south bank of the Potomac River forms the District's border with Virginia and has two major tributaries: the Anacostia River and Rock Creek. Tiber Creek, a natural watercourse that once passed through the National Mall, was fully enclosed underground during the 1870s. The creek also formed a portion of the now-filled Washington City Canal, which allowed passage through the city to the Anacostia River from 1815 until the 1850s. The Chesapeake and Ohio Canal starts in Georgetown and was used during the 19th century to bypass the Little Falls of the Potomac River, located at the northwest edge of Washington at the Atlantic Seaboard fall line.The highest natural elevation in the District is 409 feet (125 m) above sea level at Fort Reno Park in upper northwest Washington. The lowest point is sea level at the Potomac River. The geographic center of Washington is near the intersection of 4th and L Streets NW.The District has 7,464 acres (30.21 km2) of parkland, about 19% of the city's total area and the second-highest percentage among high-density U.S. cities. This factor contributed to Washington, D.C., being ranked as third in the nation for park access and quality in the 2018 ParkScore ranking of the park systems of the 100 most populous cities in the United States, according to the nonprofit Trust for Public Land.The National Park Service manages most of the 9,122 acres (36.92 km2) of city land owned by the U.S. government. Rock Creek Park is a 1,754-acre (7.10 km2) urban forest in Northwest Washington, which extends 9.3 miles (15.0 km) through a stream valley that bisects the city. Established in 1890, it is the country's fourth-oldest national park and is home to a variety of plant and animal species, including raccoon, deer, owls, and coyotes. Other National Park Service properties include the C&O Canal National Historical Park, the National Mall and Memorial Parks, Theodore Roosevelt Island, Columbia Island, Fort Dupont Park, Meridian Hill Park, Kenilworth Park and Aquatic Gardens, and Anacostia Park. The D.C. Department of Parks and Recreation maintains the city's 900 acres (3.6 km2) of athletic fields and playgrounds, 40 swimming pools, and 68 recreation centers. The U.S. Department of Agriculture operates the 446-acre (1.80 km2) U.S. National Arboretum in Northeast Washington.
Student:
What is the country's fourth-oldest national park?