Which of the following is true?
a. humans cannot sense stimuli below the absolute threshold.
b. humans cannot be affected by stimuli below the absolute threshold at all.
c. stimuli presented below the absolute threshold can have a subtle, brief effect on behavior.
d. stimuli presented below the absolute threshold exert a strong, powerful effecton behavior.

C. Stimuli presented below the absolute threshold can have a subtle, brief effect on behavior.

Explanation:

The absolute threshold is simply the stimulation necessary for a stimulus to cause a specific sensation, such as light, sound, taste, pressure, or odor 50% of the time.

Despite being considered a limiting factor, it is possible to perceive stimuli below the absolute threshold. Because it is a point where we detect a stimulus half of the time, so exactly at the threshld or below it, it is still possible to detect a stimulus eventually.