Which of the Following Concerning the Use of Facial Electromyography

Which of the following concerning the use of facial electromyography (EMG) to assess attitudes is true?

A) Facial EMG can detect muscular changes not observable to the naked eye.
B) Facial EMG does not provide information about the direction of attitudes.
C) One problem with using facial EMG is that the same pattern of activity could be interpreted as happiness or sadness.
D) Facial EMG is only an accurate measure of attitudes if people know their attitudes are being assessed, so it is susceptible to the same social desirability biases as self-reports.