Fiona and her fellow green committee members are studying the effects of the use of energy-efficient light bulbs. which of these might their study include?

Their study might include determining the pros and cons of using the light bulbs.
After they've determined the good sides of using energy-efficient light bulbs, and the bad sides, they will certainly know the effects that these bulbs produce. Therefore they will decide whether it is a good idea to use them or to move on to something else.