Which activity is involved in contour farming? 

A)  plowing across the slope 
B)  plowing straight down a slope or straight up a slope 
C)  building a series of small dams 
D)  converting a steep slope into a series of terraces

Which habitat do humans know little about? 

A)  deep ocean basins 
B)  Antarctica 
C)  deep space 
D)  tropical rainforests

A major goal of the wise-use movement was to weaken or repeal most of the US environmental laws and regulations.

Which of the following processes has added heat to Earth's interior during or after its formation?

A) collision of asteroids and meteoroids with Earth
B) formation and sinking of masses of iron and nickel
C) radioactive decay
D) all of these