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 (", ").

Paragraph- Sent 1: Feel the top of your desk.
Sent 2: Does it look and feel smooth?
Sent 3: Yes, it feels and looks smooth, but is it really?
Sent 4: Even when surfaces look smooth to the unaided eye, they may not be.
Sent 5: Scientists use a microscope to look at things more closely.
Sent 6: Through a microscope, smooth surfaces may appear rough or bumpy.
Sent 7: Look at the metal surfaces in Figure 1.8.
Sent 8: The metal foil is so smooth that it is shiny.
Sent 9: However, when highly magnified, it is clearly not smooth.
Sent 10: It actually looks to be very bumpy.
Sent 11: All those bumps grab the bumps of other surfaces.
Sent 12: They grind together.
Sent 13: They oppose the motion of the two surfaces.
Sent 14: Now you know what causes friction.
Question: What is it called when the motion of two surfaces together is opposed?.
13, 14.

Paragraph- Sent 1: For much of the world, the Algarve is synonymous with Portugal, yet the Portuguese will tell you the exact opposite: the region has little in common with the rest of the country.
Sent 2: The southern stretch of coast is more reminiscent of a North African landscape than a European one.
Sent 3: It has no cosmopolitan cities, like Lisbon and Porto, which are farther north.
Sent 4: Most of Portugal is known for quaint towns, medieval castles, and grand palaces.
Sent 5: The Algarve is more recognizable for impenetrable blocks of tourist apartments, hotels, and meticulously manicured golf courses.
Sent 6: And beaches.
Sent 7: Think Algarve and the mind pictures long, glorious stretches of golden sands, secluded coves framed by odd ochre-colored rock formations, and deep green waters.
Sent 8: With about 160 km (100 miles) of coastline, Portugal's southern province is one of Europe's premier beach destinations.
Sent 9: The occasionally chilly ocean is the Atlantic, but the Algarve has a sultry Mediterranean feel.
Sent 10: Its consistent climate is the best in Portugal, and one of the kindest in the world: more than 250 days of sunshine a yearmore than almost any other international resort area.
Sent 11: The moderating effect of the Gulf Stream produces a fresh springtime breeze throughout winter, and in late January and February, white almond blossoms blanket the fields.
Sent 12: In summer the heat is intense but rarely unbearable, and regardless, beautiful beaches and innumerable pools are always just a dive away.
Sent 13: Magnificent year-round weather has made the Algarve a huge destination for sporting vacations.
Sent 14: Superb golf facilities aboundseveral with tees dramatically clinging to cliffs and fairways just skirting the edge of the oceanand horseback riding, tennis, big-game fishing, sailing, and windsurfing are immensely popular.
Sent 15: Sports, beaches and hospitable weathernot to mention easily organized package vacationsare surely the reasons the Algarve receives as many visitors as the rest of Portugal in its entirety.
Sent 16: But it's not just international tourists that descend on the Algarve; many Portuguese from Lisbon and elsewhere in the north have holiday homes and spend their summer vacations here.
Sent 17: The coast is neatly divided into the rugged Barlavento to the west and the flat beauty of Sotavento to the east.
Sent 18: West is where you'll find the famous orange cliffs and surreal eroded rock stacks.
Question: Which region of Portugal gets the most sunshine on an average year?.
9, 10.

Paragraph- Sent 1: Three years after the events of the original film , the authorities are attempting to return law and order to ravaged District 13 .
Sent 2: The death of gang overlord Taha Ben Mahmoud has left a power vacuum , and total control of the area is now being fought over by five rival territorial gang lords who want to step into Taha 's position .
Sent 3: After taking out a major drug dealer , Damien is framed for drug dealing and arrested , but manages to make a call to Le to .
Sent 4: Meanwhile , corrupt government agents from the Department of Internal State Security , led by Gassman are bent on destroying the five tower blocks at the heart of District 13 with tactical precision bombing , and building luxury flats after the area is cleared .
Sent 5: In order to spark conflict with the district 's gangs , they shoot several cops , dump their car in District 13 , and prompt several gang members into gunning down the vehicle .
Sent 6: The footage of the incident convinces the President to carry out the strike .
Sent 7: However , a group of teens videotaped the agents as they shot the cops themselves .
Sent 8: The DISS agents soon come after the teen to arrest him and seize the recording , but the youth manages to slip his memory card to Le to .
Sent 9: Le to escapes the cops in District 13 and goes to rescue Damien .
Sent 10: After freeing Damien from his cell , they discuss the events and further plans , resolving to gather enough proof to expose the DISS agents .
Sent 11: While Damien distracts the guards , Le to breaks into Gassman 's office to steal his hard-drive for the evidence that they need .
Question: Who steal hard-drive from Gassman 's office?.
10, 11.