Question: Which country hosted the 1920 Summer Olympics, where the country containing Roma metro station took part?

full_context: Document 1: Portugal at the 1920 Summer Olympics: Portugal competed at the 1920 Summer Olympics in Antwerp, Belgium. A delegation of thirteen competitors participated in two sports, however no medals were won.
Document 2: Spagna (Rome Metro): Spagna is an underground station on Line A of the Rome Metro, which was inaugurated in 1980. It is situated in the rione Campo Marzio and is named after the nearby Piazza di Spagna.
Document 3: Portugal: The two largest metropolitan areas have subway systems: Lisbon Metro and Metro Sul do Tejo in the Lisbon Metropolitan Area and Porto Metro in the Porto Metropolitan Area, each with more than 35 km (22 mi) of lines. In Portugal, Lisbon tram services have been supplied by the Companhia de Carris de Ferro de Lisboa (Carris), for over a century. In Porto, a tram network, of which only a tourist line on the shores of the Douro remain, began construction on 12 September 1895 (a first for the Iberian Peninsula). All major cities and towns have their own local urban transport network, as well as taxi services.
Document 4: Switzerland at the 1920 Summer Olympics: Switzerland competed at the 1920 Summer Olympics in Antwerp, Belgium. 77 competitors, all men, took part in 45 events in 13 sports.
Document 5: Athletics at the 1920 Summer Olympics: At the 1920 Summer Olympics held in Antwerp, 29 athletics events were contested, all for men only. The competitions were held from August 15, 1920 to August 23, 1920.
Document 6: Lisbon Metro: The Lisbon Metro () is the rapid transit system of Lisbon, Portugal. Opened in December 1959, it was the first subway system in Portugal.
Document 7: Cabo Ruivo (Lisbon Metro): Cabo Ruivo is a station on the Red Line of the Lisbon Metro. The station is located on Av. Padua, near the intersection with Av. Infante Dom Henrique serving the Cabo Ruivo area of the city.
Document 8: Norway at the 1920 Summer Olympics: Norway competed at the 1920 Summer Olympics in Antwerp, Belgium. 194 competitors, 188 men and 6 women, took part in 72 events in 16 sports.
Document 9: Portugal: By the early 1970s Portugal's fast economic growth with increasing consumption and purchase of new automobiles set the priority for improvements in transportation. Again in the 1990s, after joining the European Economic Community, the country built many new motorways. Today, the country has a 68,732 km (42,708 mi) road network, of which almost 3,000 km (1,864 mi) are part of system of 44 motorways. Opened in 1944, the first motorway (which linked Lisbon to the National Stadium) was an innovative project that made Portugal among one of the first countries in the world to establish a motorway (this roadway eventually became the Lisbon-Cascais highway, or A5). But, although a few other tracts were created (around 1960 and 1970), it was only after the beginning of the 1980s that large-scale motorway construction was implemented. In 1972, Brisa, the highway concessionaire, was founded to handle the management of many of the regions motorways. On many highways, toll needs to be paid, see Via Verde. Vasco da Gama bridge is the longest bridge in Europe.
Document 10: New York City Subway: The New York City Subway is a rapid transit system owned by the City of New York and leased to the New York City Transit Authority, a subsidiary agency of the state - run Metropolitan Transportation Authority (MTA). Opened in 1904, the New York City Subway is one of the world's oldest public transit systems, one of the world's most used metro systems, and the metro system with the most stations. It offers service 24 hours per day on every day of the year.
Document 11: Sweden at the 1920 Summer Olympics: Sweden competed at the 1920 Summer Olympics in Antwerp, Belgium. 260 competitors, 247 men and 13 women, took part in 100 events in 18 sports.
Document 12: List of metro systems: This list of metro systems includes electrified rapid transit train systems worldwide. In some cases, metro systems are referred to as subways, U-Bahns or undergrounds. As of October 2014, 157 cities in 55 countries around the world host the approximately 160 metro systems that are listed here. The London Underground first opened as an ``underground railway ''in 1863 and its first electrified underground line opened in 1890, making it the world's first metro system. The metro system with the longest route length is the Shanghai Metro; the busiest one is the Beijing Subway; and the one with the most stations is the New York City Subway.
Document 13: El Metropolitano: El Metropolitano is a new Bus rapid transit system serving the city of Lima, Peru. Its construction began in the year 2006 during Luis Castañeda Lossio's period as Mayor of Lima.
Document 14: Roma (Lisbon Metro): Roma is a station on the Green Line of the Lisbon Metro. The station is located on Avenida de Roma, near the intersection with Av. dos Estados Unidos da América, enabling access to the Roma-Areeiro railway station nearby.
Document 15: Campo Grande (Lisbon Metro): Campo Grande is an elevated interchange station on the Yellow and Green Lines of the Lisbon Metro. It has a large bus terminal at ground level and is located on Rua Cipriano Dourado just north of Avenida General Norton de Matos in the Lisbon parish of Campo Grande.
ground_truth: Belgium
sub_queries: Roma >> part of Answer: Lisbon Metro
Lisbon Metro >> country Answer: Portugal
Portugal at the 1920 Summer Olympics >> country Answer: Belgium