Which of the following is the best definition of an independent variable?
a. the variable that is changed on purpose in an experiment
b. the variable that is changed as a result to some action taken by the scientist
c. the variable that must be held constant throughout the experiment
d. a mathematical model (an equation)

how to make a simple air condition

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.

c (diamond),

sio2 (quartz)

d) a person who learns about the world by observing it.

explanation:

scientist are people who discover why and how things are done and made in the world.