A researcher wants to test if juvenile hormone (similar to testosterone) is associated with aggression in paper wasps. The researcher films wasp interactions between wasp pairs in which one individual is given extra juvenile hormone. The researcher also films wasp interactions between pairs in which neither individual is given extra testosterone. Filming conditions are the same for each pair and the level of aggression is recorded. What is the control in this experiment?
a. The pairs in which one individual is given extra juvenile hormone is the control.
b. The pairs in which neither individual is given extra juvenile hormone is the control.
c. There is no control; this is an observational study.
d. The similar filming conditions is the control.

This is an experiment in which the researcher wants to establish a relation between the aggresion in wasp with the juvenile hormone, but to know which are really the effects you need something to compare with, that is called the control group, that is usually in the normal conditions, in this case it corresponds to the pairs in which they don't give the extra juvenile hormone, so the researcher can compare the difference between this pair with the pair in which one of the individuals has extra juvenile hormone.