Input: Read this: Asphalt/bitumen is typically stored and transported at temperatures around 150 C (302 F). Sometimes diesel oil or kerosene are mixed in before shipping to retain liquidity; upon delivery, these lighter materials are separated out of the mixture. This mixture is often called "bitumen feedstock", or BFS. Some dump trucks route the hot engine exhaust through pipes in the dump body to keep the material warm. The backs of tippers carrying asphalt/bitumen, as well as some handling equipment, are also commonly sprayed with a releasing agent before filling to aid release. Diesel oil is no longer used as a release agent due to environmental concerns.
Question: To retain liquidity, what is sometimes mixed in with engine exhaust?

Output: unanswerable

Input: Read this: Miami International Airport and PortMiami are among the nation's busiest ports of entry, especially for cargo from South America and the Caribbean. The Port of Miami is the world's busiest cruise port, and MIA is the busiest airport in Florida, and the largest gateway between the United States and Latin America. Additionally, the city has the largest concentration of international banks in the country, primarily along Brickell Avenue in Brickell, Miami's financial district. Due to its strength in international business, finance and trade, many international banks have offices in Downtown such as Espirito Santo Financial Group, which has its U.S. headquarters in Miami. Miami was also the host city of the 2003 Free Trade Area of the Americas negotiations, and is one of the leading candidates to become the trading bloc's headquarters.
Question: What is Florida's busiest seaport?

Output: unanswerable

Input: Read this: Law enforcement, however, constitutes only part of policing activity. Policing has included an array of activities in different situations, but the predominant ones are concerned with the preservation of order. In some societies, in the late 18th and early 19th centuries, these developed within the context of maintaining the class system and the protection of private property. Many police forces suffer from police corruption to a greater or lesser degree. The police force is usually a public sector service, meaning they are paid through taxes.
Question: When were police used to protect the class system?

Output: late 18th and early 19th centuries

Input: Read this: Similar examples abound. Macedonian, although mutually intelligible with Bulgarian, certain dialects of Serbian and to a lesser extent the rest of the South Slavic dialect continuum, is considered by Bulgarian linguists to be a Bulgarian dialect, in contrast with the contemporary international view and the view in the Republic of Macedonia, which regards it as a language in its own right. Nevertheless, before the establishment of a literary standard of Macedonian in 1944, in most sources in and out of Bulgaria before the Second World War, the southern Slavonic dialect continuum covering the area of today's Republic of Macedonia were referred to as Bulgarian dialects.
Question: When was a standard of Serbian developed in Macedonia?

Output:
unanswerable