In order to get around the human ability to mask emotions and more clearly define facial expressions for particular emotions, Paul Ekman and his associates:

a. developed a special coding system that analyzed and identified the numerous facial muscles.
b. developed an inter-observer system to make sure that observers defined expressions reliably.
c. interviewed all participants in order to assess unexpressed feelings and motivations.
d. monitored the brain waves of participants to determine which hemisphere had higher activation.

A