You walk outside on a sunny day and have to squint until you put sunglasses on. What is the stimulus that causes the response of squinting? the outside temperature the bright sunlight the surrounding air

The correct answer is: the bright sunlight.

Explanation:

The bright sunlight on a sunny day is the stimulus that causes the response of squinting, which is necessary for us to protect our eyes from different conditions that can be caused by extreme sun exposure.

This stimulus is transmitted to the Central Nervous System by sensory neurons, so the information can be processed in the brain and the response to squint our eyes to receive less light can be performed by the orbicularis oculi muscle (the one that closes the eyelids).