A tentative prediction about the relationship between two variables is: A. a confounding of variables. B. an operational definition. C. a theory. D. a hypothesis.

For this exercise, go through each term provided in the options and understand their meaning in the context of scientific research. A. Confounding of variables: This refers to a situation where an external factor affects the relationship between the independent and dependent variables, making it difficult to determine the true effect of the independent variable on the dependent variable. B. Operational definition: An operational definition is a clear and specific description of how a variable will be measured or manipulated in a study. C. Theory: A theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. D. Hypothesis: A hypothesis is a tentative and testable statement about the relationship between two or more variables, which can be either supported or refuted through scientific research.

Now that you have an understanding of the provided terms, it's time to identify which one fits the description of a tentative prediction about the relationship between two variables. As a hypothesis is a tentative and testable statement about the relationship between two or more variables, it is the correct answer. So the answer for this exercise is: D. a hypothesis.