NASA catalogs near-Earth-objects (NEOs) that are larger than ____ in diameter and come within about 75 million km of Earth
a. 10 m
b. 100 m
c. 1 km
d. 5 km
e. 15 km
ANSWER: b
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An oxygen sag curve occurs when
a. Fish population numbers sag. b. Heavy metals that have entered a stream bind oxygen molecules and remove them from the available oxygen supply. c. The breakdown of biodegradable wastes by bacteria lowers the available oxygen in the water for organisms with high oxygen requirements. d. Carbon dioxide values exceed dissolved oxygen values. e. Oxygen content in the air around a particular body of water becomes slightly lower than normal
Carcinogens may be difficult to identify because ________
A) there is no way to measure the carcinogenic potential of a substance B) they are the least common toxicants C) there is a long lag time between exposure to the agent and disease D) they are rare in nature E) most are invisible
The most important attribute of Earth is that it is a(n) _______________ system, providing the precise combinations of objects and characteristics to permit the existence of life
Fill in the blank(s) with correct word
The solum or true soil includes all horizons above the C-horizon
Indicate whether the statement is true or false