When sanjay recognizes line segments and areas of light and dark as his friend's face at an airport gate, he is demonstrating: ?

The answer is "he i demonstrating perception."
When you see the expressions on someones face and understand or  have an idea about the situation, or when you aware of something by using your sense, this is known as perception. So, perception is the way in which you understand something by using your senses as sanjay takes an idea by looking at his friend's face.

Sheet stain on pee wee's sheets