The Primary Drawback to Using Either the Electroencephalograph (EEG) or the Magnetoencephalograph

The primary drawback to using either the electroencephalograph (EEG) or the magnetoencephalograph (MEG) technique to study brain activity is that these techniques

A) record precisely where the brain is active, but not the amount of ongoing activity.
B) expose the brain to radioactivity.
C) record ongoing brain activity, but not the precise location of the activity.
D) require invasive surgery to implant the electrodes.