40. Why was Zachary Taylor chosen by his party as a candidate for president?
41. According to the speakers, why is it surprising that Taylor was elected president?
42. Why did Taylor accomplished¹ relatively² little as president?
43. What will the class probably do next?

Q44-46 A talk at a special event.
I want to welcome each and every balloon enthusiast³ in Philadelphia. Thank you for coming here this morning to commemorate⁴ the first balloon voyage in the United States. On January 9th, 1793, at 10 o'clock in the morning, a silk balloon lifted into the skies above this city, which was at that time the capital of the country. According to the original records of the flight, the voyage lasted 46 minutes, from its departure in Philadelphia to its landing across the Delaware river in New Jersey⁵. Though our pilots today will try to approximate the original landing site, they are at the mercy of the winds. So who knows where they will drift off to. Even the balloonist in 1793 experienced some uncertain weather that
day, there were clouds, fog and mist in various directions. Our reenactment promises to be nothing less than spectacular. The yellow balloon directly behind me is 5 stories high. It's inflated⁶ with helium unlike the original, which was filled with hydrogen and unbeknownst to the pilot, potentially explosive. Gas filled models are pretty uncommon⁷ now because of the extremely high cost so the 80 other balloons in today's launch are hot air, heated by propane burners. These balloons are from all over the country.
44. What is the purpose of the balloon launch?
45. What problem might today's pilots encounter?
46. What does the speaker imply about helium balloons?

Q47-50 Lecture in a geology class.
I'm glad you've brought up the question of our investigations⁸ into the makeup⁹ of the earth's interior. In fact since this is the topic in your reading assignment for next time, let me spend these last few minutes of class talking about it. There were several important discoveries in the early part of this century that helped geologists¹⁰ develop a more accurate picture of the earth's interior. The first key discovery had to do with seismic¹² waves. Remember they are the vibrations¹³ caused by earthquakes. Well, scientists found that they travel thousands of miles through the earth's interior. This finding enabled geologists to study the inner parts of the earth. You see, the studies revealed that these vibrations were of two types: compression or P waves and shear¹⁴ or S waves. And researchers found that P waves travel through both liquids and solids while S waves travel only through solid matter. In 1906, a British geologist¹¹ discovered that P waves slowed down at certain depth but kept traveling deeper. On the other hand, S waves either disappeared or were reflected back. So he concluded that the depth marked the boundary between a solid mantle¹⁵ and a liquid core. Three years later, another boundary was discovered that between the mantle and the earth's crust. There are still a lot to be learned about the earth. For instance, geologists know that the core is hot. Evidence of this is the molten lava¹⁶ that flows out of the volcanoes. But we are still not sure what source of the heat is.
47. What is the purpose of the talk?
48. What important discovery about seismic waves does the instructor¹⁷ mention?
49. What did the study of seismic vibrations help geologists learn more about?
50. What did P and S waves help scientists discover about the layers of the earth?