. Dr. Wongo is doing a psychophysical experiment to determine the smallest concentration of coffee that we can detect by olfaction. In the experiment, he presents some coffee concentrations that are clearly detectable, others that cannot be detected, and some that are just detectable. These presentations are randomized. Dr. Wongo can be said to be using the method of: a. Adjudication b. Constant stimuli c. Inverse thresholds d. Limits