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The Timber rattlesnake, once widespread throughout the eastern United States, is now on the endangered species list and is extinct in two eastern states in which it once thrived. Compared to its western cousins, the Timber rattlesnake may be especially vulnerable because 5 of certain behaviors adapted for coping with the cold climate in which it lives.

Rattlesnakes are generally found in warm climates because, like all reptiles, they cannot generate or regulate their own body temperature 10 internally and must rely on the sun’s warmth for heat. But Timber rattlesnakes migrated into colder northern areas about 8,000 years ago when glaciers retreated. In these northern regions, the snakes developed a number of adaptive strategies to survive, but ultimately these behaviors make them more vulnerable to human predation, their 15 main threat.

One survival strategy the snakes have developed is hibernation. For approximately eight months of the year, the rattlers remain motionless in deep frost-free crevices, with their body temperature dropping 20 as low as 40 degrees. In the spring when they emerge, they must warm their chilled bodies by sunning for three or four days on rocks in the open. This behavior, coupled with the fact that Timber rattlesnakes tend to concentrate in large numbers at their wintering sites, makes them easy prey. Gestating females are particularly vulnerable because 25 they spend much of their time basking in the sun in order to produce live young from eggs. In addition, females have very long interbirth intervals, producing live young only every three to five years. If a frost or cold spell comes late in the year, the entire litter of six to twelve young may die.

30 Efforts are underway to protect the Timber rattlesnake and its habitat from further human depredation, but in many states it is already too late.

1. What is the main topic of the passage?

2. Which of the following is closest in meaning to the word “vulnerable” in line 4?

3. Which of the following is true about Timber rattlesnakes?

4. In line 19, the word “crevices” could be replaced by which of the following?

5. Which of the following could best replace the word “emerge” in line 20?

6. In which of the following places might a person be most likely to find Timber rattlesnakes in the spring?

7. Which of the following could best replace the phrase “coupled with” in line 22?

8. The phrase “easy prey” in line 24 could best be replaced by which of the following?

9. Which of the following words can best replace the word “basking” in line 25?

10. According to the passage, which of the following does NOT contribute to the rattlesnake being an endangered animal?

11. Which of the following could best replace the word “depredation” in line 32?

12. What is the author’s tone attitude toward the topic?