(A) says, "a positive reading is just as reliable an indicator of the absence of temporal lobe epilepsy"
(A) does not logically complete the argument because it's not properly characterizing the stimulus because the stimulus tells us that a positive reading is evidence of epilepsy. Thus, (A) is out.
(D) says, "a negative reading does not mean that temporal lobe epilepsy can be ruled out"
(D) works to complete the conclusion in the stimulus because it has to be true. Sometimes the EEG does not catch the signs of epilepsy, and in these types of cases, the EEG reading would show a false negative. Thus, (D) is the correct answer choice.
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