1. Many birds will, in the normal course of their migrations, flying more than three thousand miles to reach their winter homes.

2. Heartburn can best be understood as a symptom causing by acid reflux due to a weak lower esophageal sphincter.

3. Some gorillas beat their chests as an express of high spirits.

4. Air pollution, together with littering, are causing many problems in our large, industrial cities today.

5. In 1927 Charles Lindbergh was the first to fly solo nonstop from New York to Paris in such short time.

6. He has been hoped for a raise for the last four months, but his boss is reluctant to give him one.

7. Industrialist Henry Ford introduced assembly-line techniques into the manufacturer of motor vehicles.

8. Aristotle systematically set out the various forms of the syllogism that has remained an important reference for logic.

9. Salmon lay their eggs and die in freshwater, although they live in salt water when most of their adult lives.

10. The understanding electricity depends on a knowledge of atoms and the subatomic particles of which they are composed.

11. Dorothea Dix worked extensively during the second half of the nineteenth century to improve condition in mental health facilities and the prisons.

12. As television images of the astronauts showed, even for trained professionals who are used to move about in a lessened gravitational field, there are still problems.

13. Because the interstate highway system linking roads across the country was built about thirty-five years ago, most of the roads in the system now need repaired.

14. The soil is composed of a mixture of organic matter called humus and inorganic matter derived from rocks.

15. Crocodiles different from alligators in that they have pointed snouts and long lower teeth that stick out when their mouths are closed.

16. Perhaps the colonists were looking for a climate like England, when they decided to settle the North American continent instead of the South American continent.

17. Ghost towns like Rhyolite, Nevada are communities that are not longer inhabited because changes in economic conditions have caused the people to move elsewhere.

18. Into among the five Great Lakes, only Lake Michigan is located entirely within the territorial boundaries of the United States.

19. The two types of nucleic acids, known as DNA and RNA, are not the alike.

20. This new model not only saves time but also energy by operating on two batteries instead of four.