Detailed Instructions: 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 (", ").
See one example below:
Problem: Paragraph- Sent 1: A Republican bid to keep the government open past Friday includes no new money for the construction of a border wall along the U.S.-Mexico border, according to several congressional aides familiar with ongoing talks.
Sent 2: GOP leaders submitted the new offer Tuesday afternoon in an effort to appease Democrats, whose votes are needed to avert a shutdown of federal agencies, several House and Senate aides said.
Sent 3: However, Republicans also insisted on increases in border security and defense spending, including money to repair existing fencing and new surveillance technology to patrol the nearly 2,000-mile border.
Sent 4: Democrats have indicated that they would support such appropriations so long as no money goes toward an actual wall.
Question: Who has to be appeased to keep the government open?.
Solution: 1, 2.
Explanation: The question is: Who has to be appeased to keep the government open? The phrase "appease Democrats" is mentioned in Sent 2, about accepting offer that is mentioned in Sent 1 to "keep the government open". So, Sent 1 and Sent 2 are the sentences needed to answer this question.

Problem: Paragraph- Sent 1: At 9:48, a representative from the White House shelter asked if there were any indications of another hijacked aircraft.
Sent 2: The deputy director for operations mentioned the Delta flight and concluded that "that would be the fourth possible hijack."Sent 3: At 9:49, the commander of NORAD directed all air sovereignty aircraft to battle stations, fully armed.
Sent 4: At 9:59, an Air Force lieutenant colonel working in the White House Military Office joined the conference and stated he had just talked to Deputy National Security Advisor Stephen Hadley.
Sent 5: The White House requested (1) the implementation of continuity of government measures, (2) fighter escorts for Air Force One, and (3) a fighter combat air patrol over Washington, D.C.
Sent 6: By 10:03, when United 93 crashed in Pennsylvania, there had been no mention of its hijacking and the FAA had not yet been added to the teleconference.
Sent 7: The President and the Vice President The President was seated in a classroom when, at 9:05, Andrew Card whispered to him: "A second plane hit the second tower.
Sent 8: America is under attack."Sent 9: The President told us his instinct was to project calm, not to have the country see an excited reaction at a moment of crisis.
Sent 10: The press was standing behind the children; he saw their phones and pagers start to ring.
Sent 11: The President felt he should project strength and calm until he could better understand what was happening.
Sent 12: The President remained in the classroom for another five to seven minutes, while the children continued reading.
Sent 13: He then returned to a holding room shortly before 9:15, where he was briefed by staff and saw television coverage.
Sent 14: He next spoke to Vice President Cheney, Dr. Rice, New York Governor George Pataki, and FBI Director Robert Mueller.
Sent 15: He decided to make a brief statement from the school before leaving for the airport.
Sent 16: The Secret Service told us they were anxious to move the President to a safer location, but did not think it imperative for him to run out the door.
Sent 17: Between 9:15 and 9:30, the staff was busy arranging a return to Washington, while the President consulted his senior advisers about his remarks.
Sent 18: No one in the traveling party had any information during this time that other aircraft were hijacked or missing.
Sent 19: Staff was in contact with the White House Situation Room, but as far as we could determine, no one with the President was in contact with the Pentagon. 
Question: How was America attacked?.
Solution:
1, 2, 7, 8.