About how many asteroids larger than 1 km in diameter are known to be in Earth-crossing orbits (those that pass through Earth’s orbit around our sun)?
a. 20
b. 100
c. 500
d. 1500
e. 5200
ANSWER: d
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A garden is suffering from a quickly growing mold. The most effective treatment for this problem would be the application of
A) an herbicide. B) a fungicide. C) a pesticide. D) a rodenticide.
What is true about particulates, or aerosols?
A. They are critical to the formation of clouds. B. They have no influence on temperature. C. They are the result of human activities. D. They originate from natural sources. E. They have both solid and liquid particles.
Hydrothermal deposits are predominantly composed of what type of ore minerals?
A. oxide B. pegmatite C. evaporite D. sulfide
The world's potentially farmable land is estimated to be about ________ the present cultivated area
A) twice B) four times C) eight times D) sixteen times E) thirty-two times