Each time that subjects do math while in the scanner, brain area X is activated. Jim concludes that this area is necessary for math. Susy tells Jim that he cannot make such a claim from neuroimaging data, which are correlational. She recommended that he use the _____ technique.
A. positron emission tomography
B. electroencephalogram
C. trans-cranial magnetic stimulation
D.magnetoencephalography
E. subtraction technique of Donders