​In an experimental design that investigates the effects of a low carbohydrate diet on weight loss, diet would be

A) the independent variable.
B) ​the dependent variable.
C) ​an extraneous variable.
D) ​a placebo.

In an experimental design, the independent variable is the variable that is manipulated by the researcher in order to measure its effect on the dependent variable. In this case, the researcher is manipulating the diet (specifically, a low carbohydrate diet) and measuring its effect on weight loss. Therefore, the independent variable is diet.