The fact that you were walking with your friend at night and weren't able to see her face but her face became more visible as time went by is an example of a. contrast gain: your eyes become more sensitive to the available contrast
Contrast gain refers to the method by which the eyes adjust to the brightness around them as time goes on to allow us to see more clearly.
It works by the pupils dilating more to allow for more light to come into the eyes. This would then allow the eyes to focus on the image more clearly based on the given light it picks up.
You weren't able to see your friend at first because the pupils hadn't dilated but as soon as they began to, more light came into the eye in the process of contrast gain. As this happened, you were able to see her more clearly.
In conclusion, option A is correct.
Options for this question include:
Find out more on contrast gain at https://brainly.com/question/798280
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