TASK DEFINITION: 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 (", ").
PROBLEM: Paragraph- Sent 1: How would the universe look without gravity?
Sent 2: It would have no planets and no stars.
Sent 3: Thats how it looked when it was young.
Sent 4: When the universe was young, there was only gas and dust.
Sent 5: From this gas and dust, everything we now see was made.
Sent 6: How were stars and planets created from just gas and dust?
Sent 7: The answer is gravity.
Sent 8: The same gravity that holds you down on Earth.
Sent 9: The same force that causes your pencil to roll off your desk.
Sent 10: The same force that causes it to fall to the floor.
Sent 11: The invisible force of gravity caused dust and gas particles to be pulled together.
Sent 12: This force is what formed all the objects in our solar system.
Sent 13: This force formed the smallest moons.
Sent 14: It also formed our Sun.
Sent 15: This force caused more than just our solar system to form.
Sent 16: It caused all the other solar systems to form.
Sent 17: It caused the formation of all the galaxies of the universe.
Question: Without gravity the universe would be nothing more than?.

SOLUTION: 1, 2, 4.

PROBLEM: Paragraph- Sent 1: Force is a vector.
Sent 2: What then is a vector?
Sent 3: Think about how you would give directions to a friend.
Sent 4: You would not say, just walk half a mile.
Sent 5: The person may walk a half mile in the wrong direction!
Sent 6: More information is needed.
Sent 7: You may say, follow this particular road for a half mile.
Sent 8: You may say, look for the green house on Sumter St. In both examples, you provided a direction.
Sent 9: You also gave the distance.
Sent 10: In other words, you provided a vector.
Sent 11: You did not just give a distance.
Sent 12: Both pieces of information are needed to find a location.
Sent 13: This is just like describing forces.
Sent 14: To explain forces, both size and direction are needed.
Sent 15: Notice the girl in Figure 1.1.
Sent 16: She is pushing the swing away from herself.
Sent 17: Thats the direction of the force.
Sent 18: She can give the swing a strong push or a weak push.
Question: When you say, "Follow this particular road for a half mile," what kind of information are you providing in addition to distance?.

SOLUTION: 7, 8.

PROBLEM: Paragraph- Sent 1: (CNN) -- Champion cyclist Lance Armstrong said Wednesday the U.S. Anti-Doping Agency intends to "dredge up discredited" doping allegations against him in a bid to strip him of his seven Tour de France victories.
Sent 2: The Washington Post said it received a copy of a 15-page agency letter sent Tuesday to Armstrong and several others.
Sent 3: As a result of the allegations, Armstrong was immediately banned from competing in triathlons, a sport he took up after retiring from professional bicycling, the newspaper reported on its website.
Sent 4: Armstrong, as he has in the past, said he has never engaged in doping.
Sent 5: "Unlike many of my accusers, I have competed as an endurance athlete for 25 years with no spike in performance, passed more than 500 drug tests and never failed one," Armstrong said on his website.
Sent 6: "That USADA ignores this fundamental distinction and charges me instead of the admitted dopers says far more about USADA, its lack of fairness and this vendetta than it does about my guilt or innocence."Sent 7: Justice Department prosecutors in February said they closed a criminal investigation after reviewing allegations against Armstrong.
Sent 8: They had called witnesses to a federal grand jury in Los Angeles, but they apparently determined they lacked evidence to bring a charge that Armstrong used performance-enhancing drugs.
Sent 9: Armstrong was accused of using such drugs by other riders, but never failed a drug test.
Sent 10: "These are the very same charges and the same witnesses that the Justice Department chose not to pursue after a two-year investigation," Armstrong said Wednesday.
Sent 11: According to the Post, the U.S. Anti-Doping Agency alleged it collected blood samples from Armstrong in 2009 and 2010 that were "fully consistent with blood manipulation including EPO use and/or blood transfusions."Sent 12: The allegations were previously unpublicized, according to the Post.
Sent 13: Opinion: Why fans shouldn't forgive Armstrong The letter says Armstrong and five former cycling team associates engaged in a doping conspiracy from 1998 to 2011, the Post reported.
Sent 14: Riders will testify that Armstrong used EPO, blood transfusions, testosterone and masking agents, and that he distributed and administered drugs to other cyclists from 1998 to 2005, the Post quoted the letter as saying.
Question: What does USADA stand for?.

SOLUTION:
1, 6, 11.