In this task, you're given a question, along with a context passage which has extra information available on certain terms mentioned in it. Your job is to determine which sentence(s) from the passage can be used to search for further information needed to answer the question.
Q: Question: What are the current population of the two countries that were once part of Continental Europe through an unbroken, linked ridge? Passage:The Channel is of geologically recent origin, having been dry land for most of the Pleistocene period. Before the Devensian glaciation (the most recent glacial period, which ended around 10,000 years ago), Britain and Ireland were part of continental Europe, linked by an unbroken WealdArtois anticline, a ridge that acted as a natural dam holding back a large freshwater pro-glacial lake in the Doggerland region, now submerged under the North Sea. During this period the North Sea and almost all of the British Isles were covered by ice. The lake was fed by meltwater from the Baltic and from the Caledonian and Scandinavian ice sheets that joined to the north, blocking its exit. The sea level was about lower than it is today. Then, between 450,000 and 180,000years ago, at least two catastrophic glacial lake outburst floods breached the WealdArtois anticline.

A:
Before the Devensian glaciation (the most recent glacial period, which ended around 10,000 years ago), Britain and Ireland were part of continental Europe, linked by an unbroken WealdArtois anticline, a ridge that acted as a natural dam holding back a large freshwater pro-glacial lake in the Doggerland region, now submerged under the North Sea