The correct answer is D. economically plausible.
An independent variable is a variable that is changed by the experimenter to test its effect on another variable, called the dependent variable. The relationship between the independent and dependent variables must be economically plausible, meaning that it is possible for the independent variable to have a real-world effect on the dependent variable.
For example, in an experiment to test the effect of fertilizer on plant growth, the independent variable would be the amount of fertilizer applied to the plants. The dependent variable would be the height of the plants. It is economically plausible that the amount of fertilizer applied to a plant would affect its height, because fertilizer is a nutrient that plants need to grow.
The other options are incorrect. A general ledger is a bookkeeping system that records all of a company’s financial transactions. A non-achievable relationship is a relationship that is not possible to achieve. A non-measurable relationship is a relationship that cannot be measured.