Which of the following describes an independent variable a) the variable is an experiment that is manipulated by the scientist. b) the variable is an experiment that responds to the test variable. c) the variable in an experiment that is not allowed to change d) the variable is an experiment that is controlled for all groups

Option A would be correct. The independent variable is the part and/or variable of the experiment that changes. It is what the conductor of the experiment changes, in order to test out the Dependent Variable, (which is), the part of the experiment that does not change.  The dependent variable is the variable being tested and measured in a scientific experiment.

~Lauv