Definition: 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.
Input: Passage: Because of the 1932 Byrd Road Act, the state government controls most of Virginia's roads, instead of a local county authority as is usual in other states. As of 2018, the Virginia Department of Transportation owns and operates 57,867 miles (93,128 km) of the total 70,105 miles (112,823 km) of roads in the state, making it the third largest state highway system in the United States. Although the Washington Metropolitan Area, which includes Northern Virginia, has the second highest rate of traffic congestion in the nation, Virginia as a whole has the 21st-lowest rate of congestion and the average commute time is 26.9 minutes. Virginia hit peak car usage before the year 2000, making it one of the first such states.
Virginia has Amtrak passenger rail service along several corridors, and Virginia Railway Express (VRE) maintains two commuter lines into Washington, D.C. from Fredericksburg and Manassas. VRE is one of the nation's fastest growing commuter rail services, handling nearly 20,000 passengers a day. Arlington accounted for 40% of Virginia's public transit trips as of 2013, with most of that being from the Washington Metro transit system, which also serves Alexandria  and communities in Fairfax County along I-66. The system is currently expanding west into additional areas of Loudoun County. Major freight railroads in Virginia include Norfolk Southern and CSX Transportation, the former of which is headquartered in Norfolk. Commuter buses include the Fairfax Connector and the Shenandoah Valley Commuter Bus. The Virginia Department of Transportation operates several free ferries throughout Virginia, the most notable being the Jamestown-Scotland ferry which crosses the James River in Surry County.Virginia has five major airports: Washington Dulles International and Reagan Washington National in Northern Virginia, both of which handle over 20 million passengers a year; Richmond International; and Newport News/Williamsburg International Airport and Norfolk International serving the Hampton Roads area. Several other airports offer limited commercial passenger service, and sixty-six public airports serve the state's aviation needs. The Virginia Port Authority's main seaports are those in Hampton Roads, which carried 17,726,251 short tons (16,080,984 t) of bulk cargo in 2007, the sixth most of United States ports. The Eastern Shore of Virginia is the site of Wallops Flight Facility, a rocket testing center owned by NASA, and the Mid-Atlantic Regional Spaceport, a commercial spaceport. Space tourism is also offered through Vienna-based Space Adventures.
Output:
How many public airports are in Virginia?