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.

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.