Which of the following is a common effect of OC Spray?

The involuntary closing of the eyes is indeed a common effect of OC (Oleoresin Capsicum) Spray. This spray, commonly known as pepper spray, contains active compounds that irritate the mucous membranes in the eyes, leading to immediate and intense tearing and discomfort. The overwhelming activation of the sensory neurons around the eyes results in a reflex action causing the eyelids to shut involuntarily as a protective mechanism against further irritation.

While other effects such as confusion or nausea can occur as a secondary response or from the stress of being sprayed, they are not the primary and direct physiological response to the OC spray. Delayed reaction time may also result from the disorientation caused by the spray but again is not as immediate or universally experienced as the involuntary closing of the eyes, which is a hallmark reaction to exposure to OC spray.