Katie Is Interested in How Much Lemon Juice Needs to Be

Multiple Choice

Katie is interested in how much lemon juice needs to be added to water for her friend Paul to detect it. She knows that a glass with only water (i.e., no lemon juice) will clearly be below threshold. She gives Paul this solution followed by 5 other solutions with an increasing amount of lemon juice. Paul reports being able to taste the lemon flavor at solution #4. Katie is employing the:

A) method of sensitivity
B) method of adjustment
C) method of limits
D) method of constant stimuli