Question

Which are reasons pupils dilate?

Answer 1

There are many reasons why our pupils dilate:

When pupils dilate, it usually means that there is a lack of light. Your pupils dilate so that you can get more light into your eye-sight. 

Your emotions can make your pupils dilate. They can dilate to show if we are excited, angry, happy, sad, scared, etc. They can also dilate to show how difficult the project you are working and/or thinking of. 

Studies say that your pupils also dilate when you see an attractive person. Apparently, your pupils judge if you like somebody or not really. The name for this is Bedroom Eyes. I'd tell more about this, but considering the name, you can look it up to know more. 

Another reason for your pupils to dilate is the cause of brain disease, drugs, certain medication (prescribed or not), injury to the brain, poison, such things like the listed. 

It is no doubt that the options all come together. Sadness can make your pupils dilate. Horror can. Fear and lack of light can. 

Answer: $\fbox {E: All of the above}$

Answer 2

The answer is E, all of the above. Pupils can dilate because of certain emotions and lack of light.