Final answer:
To measure the speed of pupil reaction, the time taken for the pupils to constrict should be recorded, as it assesses the pupillary light reflex.
Step-by-step explanation:
For the speed of the pupil reaction, you should record C) the time taken for the pupils to constrict. This response is directly connected to the pupillary reflex, an important aspect of neurological function that can be altered in various states of health and sympathetic nervous system activation. For instance, during a stress response such as experiencing an accident, the sympathetic nervous system stimulates the pupil dilation as part of the fight-or-flight response. Additionally, sympathetic activation leads to responses like increased heart rate and rapid breathing. However, the correct measure for the speed of the pupil reaction is the time it takes for the pupils to respond to changes in light, commonly referred to as the pupillary light reflex.