In this task you will be given an answer to a question. You need to generate a question. The answer given should be a correct answer for the generated question.

Q: The name Sulis continued to be used after the Roman invasion, leading to the town's Roman name of Aquae Sulis ('the waters of Sulis'). The temple was constructed in 60 -- 70 AD and the bathing complex was gradually built up over the next 300 years. During the Roman occupation of Britain, and possibly on the instructions of Emperor Claudius, engineers drove oak piles to provide a stable foundation into the mud and surrounded the spring with an irregular stone chamber lined with lead. In the 2nd century it was enclosed within a wooden barrel-vaulted building, and included the caldarium (hot bath), tepidarium (lukewarm bath), and frigidarium (cold bath). After the Roman withdrawal from Britain in the first decade of the 5th century, these fell into disrepair and were eventually lost due to silting up, and flooding. The Anglo-Saxon Chronicle suggests the original Roman baths were destroyed in the 6th century.

A: how old are the roman baths in bath england
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Q: In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. In terrestrial ecoregions, these are mainly plants, while in aquatic ecoregions algae predominate in this role. Ecologists distinguish primary production as either net or gross, the former accounting for losses to processes such as cellular respiration, the latter not.

A: define and compare gross primary production and net primary production
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Q: A major environmental concern known as topsoil erosion occurs when the topsoil layer is blown or washed away. Without topsoil, little plant life is possible. The estimated annual costs of public and environmental health losses related to soil erosion exceed $45 billion. Conventional agriculture encourages the depletion of topsoil because the soil must be plowed and replanted each year. Sustainable techniques attempt to slow erosion through the use of cover crops in order to build organic matter in the soil. The United States alone loses almost 3 tons of topsoil per acre per year. This is of great ecological concern as one inch of topsoil can take between 500 and 1,000 years to form naturally. On current trends, the world has about 60 years of topsoil left.

A:
when does top to bottom erosion take place
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