He has $800 to spend and wants to buy either a camera or a new photo editing software. Both the camera and the software cost $800, so he can only buy one. This illustrates the principle that:.

b. people face trade-offs.

Explanation:

Due to scarcity in the resources that we possess, i.e our resources are not infinite, we are forced to make decisions sometimes that will see us giving up something we want for another thing that we want.

This is called trade-offs and people face them all the time. This man want to wants to buy either a camera or an editor but due to the price can only buy one. He would therefore have to give up one for the other which makes this a trade-off.