1) There is evidence that prehistoric humans used fire _____ 400,000 B. C.

2) In the late 1800’s Ellen Richards, began work in the new field of “sanitary science” which was concerned with waste removal, water purification and _____ .

3) _____ red clover, high in protein content, is an extremely important leguminous hay and pasture plant of the eastern United States.

4) The topology of Mars is more _____ than that of any other planet.

5) Ostriches are _____ of living birds, attaining a height from crown to foot of about 2.4 meters and a weight of up to 136 kilograms.

6) The glaciers that reached the Pacific Coast were valley glaciers, and between those tongues of ice _____ that allowed the original forests to survive.

7) _____ orbits the Sun, Uranus rotates on its axis, an imaginary line through its center.

8) _____ duties are placed on commodities according to their value.

9) _____ about individuals who really existed and things that actually happened.

10) _____ matter in one form is transmuted to another form, a phase change is said to have taken place.

11) Noise, in the technical sense, implies a random chaotic disturbance _____ .

12) During the late 1850’s the question of the best route for the overland mail to California was _____ in the West.

13) In his book, Social Theory and Social Structure, sociologist Robert Merton explored _____ in ways that society considers abnormal.

14) _____ wooden buildings helps to protect them from damage due to weather.

15) Carbohydrates are the most abundant and _____ food sources of energy.