In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

[EX Q]: What is beneficial to London's economy?, Context: London is one of the leading tourist destinations in the world and in 2015 was ranked as the most visited city in the world with over 65 million visits. It is also the top city in the world by visitor cross-border spending, estimated at US$20.23 billion in 2015 Tourism is one of London's prime industries, employing the equivalent of 350,000 full-time workers in 2003, and the city accounts for 54% of all inbound visitor spend in UK. As of 2016 London is rated as the world top ranked city destination by TripAdvisor users.
[EX A]: Tourism

[EX Q]: How many things may mirror things with effects?, Context: The three marks of existence may reflect Upanishadic or other influences. K.R. Norman supposes that the these terms were already in use at the Buddha's time, and were familiair to his hearers.
[EX A]: three

[EX Q]: A city or area that hold boats and also allows them to load or unload cargo is called a?, Context: Logan Airport, located in East Boston and operated by the Massachusetts Port Authority (Massport), is Boston's principal airport. Nearby general aviation airports are Beverly Municipal Airport to the north, Hanscom Field to the west, and Norwood Memorial Airport to the south. Massport also operates several major facilities within the Port of Boston, including a cruise ship terminal and facilities to handle bulk and container cargo in South Boston, and other facilities in Charlestown and East Boston.
[EX A]:
Port