Answer: Option B
Step-by-step explanation:
The independent variable can be defined as the set of value or factor that is being changed ion the experiment.
Here, the experiment is to check the effect of emotion on memory. The list of words were different in the two sets of words that was given to two set of people.
One group was given emotional words and the other group was given neutral words. The conclusion was the group that were given emotional words remember more words as compared to the group given neutral words.
Hence, the independent variable is number of emotional or neutral word lists.