Giant stars
A. have already exhausted their supply of helium.
B. are close to exhausting their supply of hydrogen.
C. are close to exhausting their supply of helium.
D. have already exhausted their supply of hydrogen.
Answer: B
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Climate change and human activity like overgrazing of grasslands is leading to large areas subject to "desertification" where native grass cover dies out during drought periods, exposing soil to erosion. What is potentially the greatest initial soil erosion potential during this type of an event?
a. sand blown in from adjacent deserts b. loss of topsoil by wind erosion on a large scale c. growth of non-native shrubs shading the ground, d. further killing the grasses
Leaching ________
A) is caused by upwelling of groundwater into soils B) is a natural mechanism for adding nutrients to soils C) removes water-soluble nutrients from soils D) helps crops grow when it occurs in spring E) is a natural component of composting
The __________ cuts across the southern edge of the Sahara Desert at the widest portion of the continent.
a. Tropic of Cancer b. Tropic of Capricorn c. African Transition Zone d. none of these e. Equator
The largest zone of Earth's interior by volume is:
A. inner core B. outer core C. mantle D. crust