An Experimenter Studies the Influence of Ingesting Sugar on Memory

An experimenter studies the influence of ingesting sugar on memory. Children are randomly assigned either to eat a low calorie ice cream cone (low sugar condition) or a Ben and Jerry's cone (high sugar condition) . They are then asked to learn ten vocabulary words that they did not previously know, and the number of trials it takes to learn them is measured. The independent variable in this experiment is

A) the type of ice cream cone.
B) the number of trials to learn.
C) the number of children in each condition.
D) the differences in the children's memory.