Use a disfluent question or a proper question and find the answer to the question based on the given context or return None if an answer can't be found. A disfluent question is a question that has some interruptions in it while framing. A proper question is the correct form of the question without any disfluency.

proper question: When did the Holocene Rhine-Meuse delta stop forming? 
 disfluent question: When did the Holocene Rhine-Meuse delta influence ugh I should say stop forming? 
 context: At the begin of the Holocene (~11,700 years ago), the Rhine occupied its Late-Glacial valley. As a meandering river, it reworked its ice-age braidplain. As sea-level continued to rise in the Netherlands, the formation of the Holocene Rhine-Meuse delta began (~8,000 years ago). Coeval absolute sea-level rise and tectonic subsidence have strongly influenced delta evolution. Other factors of importance to the shape of the delta are the local tectonic activities of the Peel Boundary Fault, the substrate and geomorphology, as inherited from the Last Glacial and the coastal-marine dynamics, such as barrier and tidal inlet formations.
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proper question: Discovery of gas in the North Sea resulted in what? 
 disfluent question: Discovery of gas in Scotland no the North Sea resulted in what? 
 context: During this time, the discovery of oil in the North Sea and the following It's Scotland's oil campaign of the Scottish National Party (SNP) resulted in rising support for Scottish independence, as well as the SNP. The party argued that the revenues from the oil were not benefitting Scotland as much as they should. The combined effect of these events led to Prime Minister Wilson committing his government to some form of devolved legislature in 1974. However, it was not until 1978 that final legislative proposals for a Scottish Assembly were passed by the United Kingdom Parliament.
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proper question: How long have humans been impacting the delta for? 
 disfluent question: What has or how long have humans been impacting the delta for? 
 context: Since ~3000 yr BP (= years Before Present), human impact is seen in the delta. As a result of increasing land clearance (Bronze Age agriculture), in the upland areas (central Germany), the sediment load of the Rhine has strongly increased and delta growth has sped up. This caused increased flooding and sedimentation, ending peat formation in the delta. The shifting of river channels to new locations, on the floodplain (termed avulsion), was the main process distributing sediment across the subrecent delta. Over the past 6000 years, approximately 80 avulsions have occurred. Direct human impact in the delta started with peat mining, for salt and fuel, from Roman times onward. This was followed by embankment, of the major distributaries and damming of minor distributaries, which took place in the 11–13th century AD. Thereafter, canals were dug, bends were short cut and groynes were built, to prevent the river's channels from migrating or silting up.

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