This question seems to be incomplete. However, there is enough information to find the right answer.
Answer:
B.show the faces to all participants in one room, then move half of the participants in each group to a new room to identify faces.
Step-by-step explanation:
Context-dependent memory refers to information that is more easily recalled when the subject is in the same context where encoding and retrieval took place. Meaning, for example, that being in the same room where the patient was first introduced to a new face would make it easier for him to recognize it again. In this example, the room difference could be context-dependent, so showing the faces to all the participants in one room, and then moving half of them to a new room would be the best way to test the influence of aging on context-dependent memory effects.