Answer:
C. The child will know whether he or she used flashcards or the computer.
Explanation:
The double-blind experiment is described as an experiment in which both the individuals i.e, the person or researcher who is implementing or conducting the experiment and the participants or subjects are not being aware of the fact that which person is getting or receiving the "experimental treatment". Therefore, the main aim of the double-blind experiment is to make sure that the results of the experiment are not biased.
The correct answer is option C.