You are given a paragraph, with numbered sentences, and a question. Write the numbers of the sentences needed to answer the given question. Separate multiple sentence numbers with a comma (", "). E.g. "1, 2" would be the correct response if Sent 1 and Sent 2 are needed to answer the given question (do not include sentences that contain no information that is necessary to answer the question). Sort the sentence numbers in an increasing order (i.e., '1, 2', instead of '2, 1'). Your answer should not contain anything than the sentence numbers separated by a comma (e.g. '1, 2, 3, 4'). The given question requires more than one sentence to answer. So, your answer must contain at least one comma (", ").
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Question: Paragraph- Sent 1: Electric current cannot go through empty space.
Sent 2: Electricity needs something to flow through.
Sent 3: Electricity cannot flow through all materials.
Sent 4: Some materials resist the flow of electricity.
Sent 5: Some materials let electricity pass through easily.
Sent 6: Scientists classify these into two groups.
Sent 7: These groups are called conductors and insulators.
Sent 8: Materials that allow electrons to flow freely are called electric conductors.
Sent 9: Electricity is able to race through these materials.
Sent 10: Copper, aluminum, and steel are good conductors.
Sent 11: Materials that resist the flow of electricity are called electric insulators.
Sent 12: Instead of racing, the current may travel in slow motion, if at all.
Sent 13: Wood, rubber, and plastic are examples of electric insulators.
Sent 14: You probably know that electric wires are made of metal.
Sent 15: They typically have a rubber or plastic coating.
Sent 16: Do you know why?
Sent 17: Metals are good electric conductors.
Sent 18: They offer little resistance to electricity.
Question: Do metals offer much resistance to electricity?.

Answer: 17.

Question: Paragraph- Sent 1: Ludo Decker and Anna Gotzlowski have been living together for two years .
Sent 2: Everyday routine has set in , with Ludo neglecting his household responsibilities much to Anna 's dislike , while he is in turn annoyed by her constant complaining .
Sent 3: When Ludo runs into his former lover Marie in the disco , and Anna 's old boyfriend Ralf comes to stay in their flat for a few days , the young couple faces serious jealousy and doubt in their relationship .
Sent 4: Anna secretly reads Ludo 's phone messages , while he in turn stumbles upon '' The List '' , an account of Anna 's former lovers -- including Ralf , who scores better than Ludo does .
Sent 5: After a number of provocations , Ludo beats Ralf in a restaurant , and angrily leaves Anna .
Sent 6: Even though the two still strongly care for each other , they end up sleeping with their respective ex-lovers .
Sent 7: Ralf confesses that he never stopped loving Anna , but she rejects him and tells Ludo what happened .
Sent 8: Even though Ludo has cheated on her as well , he angrily argues that she herself told him that , unlike men , women do not actually sleep with someone without feelings being involved .
Sent 9: Anna begs him to come home , but he only says that he has no home any more , and leaves .
Sent 10: Meanwhile , Ludo 's best friend Moritz desperately tries to get more successful with women , and ends up in a number of absurd situations .
Sent 11: In the end , he meets a young and beautiful sex-addict named Lana .
Sent 12: After a few weeks , Anna receives a letter from Ludo , who has traveled back to the place where they spent their first and only vacation together .
Question: Does Ludo leave Anna as a result of discovering that Anna slept with her ex-boyfriend?.

Answer: 4, 5.

Question: Paragraph- Sent 1: A flood occurs when a river overflows its banks.
Sent 2: This might happen because of heavy rains.
Sent 3: Floodplains In very flat regions, flood water may spread out on the surface of the land.
Sent 4: It then slows down and drops its sediment.
Sent 5: If a river floods often, a floodplain develops.
Sent 6: A floodplain is an area where a thick layer of rich soil is left behind as the floodwater recedes.
Sent 7: Thats why floodplains are usually good places for growing plants.
Sent 8: They are very flat areas and they have very rich soils.
Sent 9: The Nile River valley is a great example of a floodplain.
Sent 10: Each year, the Nile River rises over its banks.
Sent 11: This floodwater carries a lot of sediment.
Sent 12: This sediment has been eroded off areas of land from upstream.
Sent 13: This sediment is dropped as the water slows down after spreading across the land.
Sent 14: What is left behind is a very rich soil.
Sent 15: Thats why crops can be raised in the middle of a sandy desert.
Sent 16: Natural Levees A flooding river often forms natural levees along its banks.
Sent 17: A levee is a raised strip of sediments deposited close to the waters edge.
Question: A flood plain is where water will spread out over flat lands slowing it down and when the water recedes what is left behind?.

Answer:
3, 6.