Answer:
A.
4Fe + 3O2 2Fe2O3 .........................
The technique to improve internal validity is D) Addition of a control group.
<h3>What is
internal validity?</h3>
Internal validity serves as the study which bring about the establishment of a trustworthy cause-and-effect relationship that can be found in treatment and an outcome.
it should be noted that Internal validity also helps to eliminate alternative explanations , hence, The technique to improve internal validity is D) Addition of a control group.
Learn more about internal validity on:
brainly.com/question/968894
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COMPLETE QUESTOIN:
Which of the following is a technique to improve internal validity ____________?
A) Experimenter expectancy
B) Participant bias
C) Use of a confederate
D) Addition of a control group
