Why does Earth have plate tectonics?
a. denser oceanic crust (relative to continental crust)
b. thicker oceanic crust (relative to continental crust)
c. relatively rapid cooling
d. convection currents and released heat deep within the mantle
e. active volcanoes (in the past and present)
d
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The tensions in each of the two supporting ropes that support Burl and Paul on opposite ends of a scaffold
A. depend on the relative weights of Burl and Paul. B. are equal. C. combine to equal zero. D. none of the above
The albedo, or reflectivity, increases (from lowest to highest) in which sequence?
A. asphalt; grassland; ocean; snow B. ocean; asphalt; grassland; snow C. asphalt; ocean; grassland; snow D. ocean; grassland; snow; asphalt E. snow; grassland; ocean; asphalt
Afghanistan is so mountainous and arid that most of the population lives in the urban areas and larger cities
Indicate whether the statement is true or false
How does the existence of densely-packed cities help preserve wilderness and rural areas?
A) The people of the wilderness form a barrier against urban dwellers and their ilk in a savage ongoing battle that spans time itself. B) Cities tend to be separated from rural areas by roads and waterways. C) Pollution is largely an urban phenomenon, so it tends to occur only near large cities, not rural areas. D) The fact that populations are unevenly distributed across the face of the Earth allows for areas that are basically empty to exist.