1.What does the professor mainly discuss?

　　a) The difference in age among American mountain ranges

　　b) The importance of a technique used for dating geological materials

　　c) The recent discovery of an ancient canyon

　　d) A comparison of various minerals used for dating

　　2.Before the use of uranium-lead analysis, where did most geologists think the Grand Canyon sandstone came from?

　　a) An ancient lake located in the American Southwest

　　b) A desert that once connected two continents

　　c) Sands carried by a river from the Appalachian Mountains

　　d) A nearby mountain range that had flattened out over time

　　3.Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.In the talk, the professor describes the sequence of uranium-lead dating.

　　Summarize the sequence by putting the events in the correct order.

　　Answer Choices

　　a) Zircon in the sandstone is matched to the zircon in a particular mountain range.

　　b) The amount of lead in sandstone zircon is measured.

　　c) The age of zircon in a sandstone sample is determined.

　　4.According to the professor, what change has caused uranium-lead dating to gain popularity recently?

　　a) It can be performed outside a laboratory.

　　b) It can now be done more efficiently.

　　c) It no longer involves radioactive elements.

　　d) It can be used in fields other than geology.

　　5.Why does the professor talk about the breaking apart of Earth's continents?

　　a) To give another example of how uranium-lead dating might be useful

　　b) To explain how the Grand Canyon was formed

　　c) To demonstrate how difficult uranium-lead dating is

　　d) To disprove a theory about the age of Earth's first mountain ranges

　　6.What does the professor imply when he says this?

　　a) The class is easier than other geology classes

　　b) The class has already studied the information he is discussing

　　c) Some students should take a course in geological dating techniques

　　d) He will discuss the topic later in the class