【正文】 s less subject to erosion. Still, their fossilization required a suite of factors: a slow rate of decay of soft tissues, little scavenging by other animals, a lack if swift currents and waves to jumble and carry away small bones, and fairly rapid burial. Given these factors, some areas have bee a treasury of wellpreserved ichthyosaur fossils. The deposits at Holzmaden, Germany, present an interesting case for analysis. The ichthyosaur remains are found in black, bituminous marine shales deposited about 190 million years ago. Over the years, thousands of specimens of marine reptiles, fish, and invertebrates have been recovered from these rocks. The quality of preservation is outstanding, but what is even more impressive is the number of ichthyosaur fossils containing preserved embryos. Ichthyosaurs with embryos have been reported from 6 different levels of the shale in a small area around Holzmaden, suggesting that a specific site was used by large numbers of ichthyosaurs repeatedly over time. The embryos are quite advanced in their physical development。 their paddles, for example, are already well formed. One specimen is even preserved in the birth canal. In addition, the shale contains the remains of many newborns that are between 20 and 30 inches long. Why are there so many pregnant females and young at Holzmaden when they are so rare elsewhere? The quality of preservation is almost unmatched, and quarry operations factors do not account for the interesting question of how there came to be such a concentration of pregnant ichthyosaurs in a particular place very close to their time of giving birth. 23. The passage supports which of the following conclusions? (A) Some species of ichthyosaurs decayed more rapidly than other species. (B) Ichthyosaur newborns are smaller than other newborn marine reptiles. (C) Ichthyosaurs were more advanced than terrestrial creatures. (D) Ichthyosaurs may have gathered at Holzmaden to give birth. 24. The word they in line 3 refers to (A) skeletons (B) scavengers (C) creatures (D) environments 25. All of the following are mentioned as factors that encourage fossilization EXCEPT the (A) speed of burial (B) conditions of the water (C) rate at which soft tissues decay (D) cause of death of the animal. 26. Which of the following is true of the fossil deposits discussed in the passage? (A) They include examples of newly discovered species. (B) They contain large numbers of wellpreserved specimens (C) They are older than fossils found in other places (D) They have been analyzed more carefully than other fossils. 27. The word outstanding in line 14 is closest in meaning to (A) extensive (B) surprising (C) vertical (D) excellent 14 28. The word site in line 17 is closest in meaning to (A) example (B) location (C) development (D) characteristic 29. Why does the author mention the specimen preserved in the birth canal (line 19)? (A) To illustrate that the embryo fossils are quite advanced in their development (B) To explain why the fossils are well preserved (C) To indicate how the ichthyosaurs died (D) To prove that ichthyosaurs are marine animals. 30. The word they in line 22 refers to (A) pregnant females and young (B) quarry operations (C) the value of the fossils (D) these factors phrase account for in line 25 is closest in meaning to (A) record (B) describe (C) equal (D) explain of the following best expresses the relationship between the first and second paragraphs? (A) The first paragraph describes a place while the second paragraph describes a field of study. (B) The first paragraph defines the terms that are used in the second paragraph. (C) The second paragraph describes a specific instance of the general topic discussed in the first paragraph. (D) The second paragraph presents information that contrasts with the information given in the first paragraph. in the passage does the author mentions the variety of fossils found at Holzmaden? (A) Line 1 (B) Lines 35 (C) Lines 1213 (D) Lines 1921 Questions 3441 The Lewis and Clark expedition, sponsored by President Jefferson, was the most important official examination of the high plains and the Northwest before the War of 1812. The President39。s secretary, Captain Meriwether Lewis, had been instructed to explore the Missouri River, and such principal streams of it as, by its course and munication with the waters of the Pacific Ocean …may offer her most direct and practicable water munication across the continent, for the purposes of merce. Captain William Clark, the younger brother of famed Gee Rogers Clerk, was invited to share the mand of the exploring party. Amid rumors that there were prehistoric mammoths wandering around the unknown region and that somewhere in its wilds was a mountain of rock salt 80 by 45 miles in extent, the two captains set out. The date was May 14, 1804. Their point of departure was the mouth of the Wood River, just across the Mississippi from the entrance of the Missouri River. After toiling up the Missouri all summer, the group wintered near the Mandan villages in the center of what is now North Dakota. Resuming their 15 journey in the spring of 1805, the men worked their way along the Missouri to its source and then crossed the mountains of western Montana and Idaho. Picking up a tributary of the Columbia River, they continued westward until they reached the Pacific Ocean, where they stayed until the following spring. Lewis and Clark brought back much new information, including the knowledge that the continent was wider than originally supposed. More specifically, they learned a good deal about river drainages and mountain barriers. They ended speculation that an easy coasttocoast route existed via the MissouriColumbia River systems, and their report