Why is air never completely dry?
a. Water vapor makes up as much as 4% of the atmosphere
b. Clouds and fog are actually liquid droplets of water
c. Water's very presence in the atmosphere accounts for dew, rain, and snow
d. All of these choices
ANS: D
The relative abundance of water vapor ensures air never is completely dry. The water vapor in the
atmosphere can condense into clouds, fog, or even rain and snow. The water vapor originates from the
ground, plants, and the sea surface. Information can be found in the section The Atmosphere Is
Composed Mainly of Nitrogen, Oxygen, and Water Vapor.
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Which statement regarding mammals is false?
A. All mammals feed their young milk. B. All mammals have nipples. C. Some mammals lay eggs. D. Marsupial mammals are born at an earlier developmental stage than placental mammals.
The monarch butterfly-milkweed relationship is best described as an example of ________
A) succession B) coevolution C) carnivory D) parasitism E) commensalism
Which of the following choices represents a rate of seafloor spreading commonly associated with a ridge such as the Mid-Atlantic Ridge?
A) 1-5 mm/yr B) 1-5 cm/yr C) 1-5 m/yr D) 1-5 km/yr
The crests of mid-oceanic ridges are associated with ________.
A. barrier reefs B. Benioff zones C. pelagic sediments D. rift valleys E. abyssal plains