Ascientist conducts an experiment to test the effects of light on earthworm activity. which is a variable in this experiment?

They're two types of variables, one being the responding the other being the controlled.
1-The controlled would be the light since the scientist would manipulate how much light the earthworm is given.
2- The responding would be the earthworm activity since it is reacting to the amount of light on it.  

There will be two Variables in this experiment:
a)  earthworm Activity 
b) Variation in the light intensity 

Some of her  assignments would be creation of drugs. she is a medical chemist after all so she'd need to have the necessary knowledge to make medicine which can later be sold in a pharmacy