An independent variable is a. directly changed by the experimenter b. manipulated by changes to the dependent variable c. a variable that is kept constant d. a variable that is used as a control

A independent variable is a variable which the experimenter can control and by changing the independent variable the experimenter observes or records the value of dependent variable.

so i see if you are asking independent than the answer is A.

if you are asking dependent variable than the answer may be B because manipulated by changes to the independent variable would be the best answer.

it would be rhyolitic hope this

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what do the different brain waves do?

explanation:

brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other. brainwaves are detected using sensors placed on the scalp. brainwave speed is measured in hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.