In this task, you are given a context, a subject, a relation, and many options. Based on the context, from the options select the object entity that has the given relation with the subject. Answer with text (not indexes).

Context: Chicago Transit Authority, also known as CTA, is the operator of mass transit in Chicago, Illinois and some of its surrounding suburbs, including the trains of the Chicago "L" and CTA bus service., The Chicago Surface Lines (CSL) was operator of the street railway system of Chicago, Illinois, from the years 1913 to 1947. The firm is a predecessor of today's publicly owned operator, the Chicago Transit Authority., North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be considered a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea., The Chicago metropolitan area, or Chicagoland, is the metropolitan area associated with the city of Chicago, Illinois, and its suburbs. With an estimated population of 9.4 million people, it is the third largest metropolitan area in the United States. Chicagoland is the area that is closely linked to the city through geographic, social, economic, and cultural ties., A county is a geographical region of a country used for administrative or other purposes, in certain modern nations. The term is derived from the Old French "conté" or "cunté" denoting a jurisdiction under the sovereignty of a count (earl) or a viscount. The modern French is "comté", and its equivalents in other languages are "contea", "contado", "comtat", "condado", "Grafschaft", "graafschap", "Gau", etc. (cf. "conte", "comte", "conde", "Graf")., The Midwestern United States, also referred to as the American Midwest or simply the Midwest, is one of the four geographic regions defined by the United States Census Bureau, occupying the northern central part of the United States of America. It was officially named the North Central region by the Census Bureau until 1984., Chicago (or ), officially the City of Chicago, is the third-most populous city in the United States, and the fifth-most populous city in North America. With over 2.7 million residents, it is the most populous city in the state of Illinois and the Midwestern United States, and the county seat of Cook County. The Chicago metropolitan area, often referred to as Chicagoland, has nearly 10 million people and is the third-largest in the U.S., Illinois is a state in the midwestern region of the United States, achieving statehood in 1818. It is the 5th most populous state and 25th largest state in terms of land area, and is often noted as a microcosm of the entire country. The word "Illinois" comes from the Algonquin word for "tribe of superior men". With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal, timber, and petroleum in the south, Illinois has a diverse economic base and is a major transportation hub. The Port of Chicago connects the state to other global ports from the Great Lakes, via the Saint Lawrence Seaway, to the Atlantic Ocean, as well as the Great Lakes to the Mississippi River, via the Illinois River. For decades, O'Hare International Airport has been ranked as one of the world's busiest airports. Illinois has long had a reputation as a bellwether both in social and cultural terms and politics., The Chicago City Railway Company ( CCRy ) was an urban transit company that operated horse , cable , and electric streetcars on Chicago 's South Side between 1859 and 1914 , when it became merged into and part of the Chicago Surface Lines ( CSL ) metropolitan - wide system . After that time it owned electric streetcars , along with gasoline , diesel , and propane - fueled transit busses . Purchased by the government agency Chicago Transit Authority ( CTA ) in 1947 , it was liquidated in 1950 ., Subject: chicago city railway, Relation: instance_of, Options: (A) airport (B) area (C) base (D) bus (E) city (F) continent (G) county (H) earl (I) four (J) geographical (K) jurisdiction (L) mass (M) metropolitan (N) metropolitan area (O) ocean (P) operator (Q) part (R) politics (S) railway system (T) region (U) river (V) sea (W) service (X) state (Y) surface (Z) system ([) the city (\) united states census
railway system