Answer:
B. amount of money that the experimental group chooses to donate.
Explanation:
Operational definition basically means how it was expressed or what it is in the context of the study. The dependent variable is the factor that is affected by the independent variable. In the study they want to see the effect of viewing pictures, so this means that "the pictures" is the independent variable. What is it that the pictures would supposedly affect then?
The tendency of for people to donate money.
The answer is then B. Amound that the experimental group chooses to donate.