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

[Q]: Which category contains a 2 year old tree?, Context: To accurately map the Amazon's biomass and subsequent carbon related emissions, the classification of tree growth stages within different parts of the forest is crucial. In 2006 Tatiana Kuplich organized the trees of the Amazon into four categories: (1) mature forest, (2) regenerating forest [less than three years], (3) regenerating forest [between three and five years of regrowth], and (4) regenerating forest [eleven to eighteen years of continued development]. The researcher used a combination of Synthetic aperture radar (SAR) and Thematic Mapper (TM) to accurately place the different portions of the Amazon into one of the four classifications.
[A]: 2

[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.
[A]: Tourism

[Q]: What were the alliances considered to be after the second punic war?, Context: This growing coalition expanded the potential enemies that Rome might face, and moved Rome closer to confrontation with major powers. The result was more alliance-seeking, on the part of both the Roman confederacy and city-states seeking membership (and protection) within that confederacy. While there were exceptions to this (such as military rule of Sicily after the First Punic War), it was not until after the Second Punic War that these alliances started to harden into something more like an empire, at least in certain locations. This shift mainly took place in parts of the west, such as the southern Italian towns that sided with Hannibal.
[A]:
empire