Helen is studying the growth of two different types of plants. She placed the same type of plant in locations with different levels of sunlight: full sun, partial shade, and full shade. For five weeks, Helen records the number of new leaves on each plant. Which of the following statements correctly describes the independent and dependent variables in Helen's experiment? * A. The independent variable is the amount of sunlight, and the dependent variable is the number of new leaves.

B. The independent variable is the kind of plant, and the dependent variable is the amount of sunlight.

C. The independent variable is the amount of sunlight, and the dependent variable is the kind of plant.

D. The independent variable is the number of new leaves, and the dependent variable is the amount of sunlight.

the earth’s crust is broken into separate pieces called tectonic plates (fig. 7.14). recall that the crust is the solid, rocky, outer shell of the planet. it is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. both types of crust rest atop solid, upper mantle material. the upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.

each tectonic plate is free-floating and can move independently. earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. the term fault is used to describe the boundary between tectonic plates. most of the earthquakes and volcanoes around the pacific ocean basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. other observable results of short-term plate movement include the gradual widening of the great rift lakes in eastern africa and the rising of the himalayan mountain range. the motion of plates can be described in four general patterns:

collision: when two continental plates are shoved together

subduction: when one plate plunges beneath another (fig. 7.15)

spreading: when two plates are pushed apart (fig. 7.15)

transform faulting: when two plates slide past each other (fig. 7.15)

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answer; quantitative versus qualitative research;