Aresearcher finds that white bread contains more preservatives and has a higher moisture content than wheat bread. she designs a test to determine whether the type of bread, white or wheat, affects the amount of mold growth. what must be done for the researcher to accurately measure the dependent variable? she will need to allow mold to grow for more days on the white bread, since it contains more preservatives, to measure the dependent variable. she will need to limit the dependent variable to white bread or wheat bread. she will need to allow mold to grow for fewer days on the white bread, since it contains more preservatives, to measure the dependent variable. she will need to learn out how to quantitatively measure mold growth to measure the dependent variable.

She will need to learn out how to quantitatively measure mold growth to measure the dependent variable.- last choices

She will need to learn out how to quantitatively measure mold growth to measure the dependent variable.

Explanation:

In any experiment there are two types of variables, dependent and independent. Independent variable is controlled by the experimenter and its value is not affected by the experiment. Dependent variable's value depends on the independent variable and is affected by the experiment.

Here, the experiment is trying to find out the way mold growth is affected by the type of bread. Hence the type of bread is the independent variable and the mold growth is dependent variable. To measure the dependent variable correctly the researcher will have to learn to quantitatively measure the mold growth. Quantitative analysis of mold growth will give an accurate measurement of dependent variable.  

the correct option is option d