Astudent conducts an experiment to see how music affects plant growth. the student obtains four identical plants. each one is potted in the same type of soil and receives the same amount of sunlight and water each day. plant a listens to classical music for three hours each day. plant b listens to rock music for three hours each day. plant c listens to country music for three hours each day. plant d does not listen to any music at all.
1. in the experiment described in the scenario, what's the variable?

a. the amount of water each plant receives
b. the amount of sunlight each plant receives
c. the type of soil in which each plant is potted
d. the type of music each plant listens to

D. The type of music each plant listens to

Explanation:

The question indicates each plant is in the same soil (so cannot be C), received the same amount of sunlight (so cannot be B) and the same amount of water (cannot be A).

However, each plant is exposed to a different type of music, one is listening classical,  another rock  and another country music.

So, the only variable in here is the type of music each plant listens to.

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.