Because most people really don't want or need to see what's in there.
If you want to, open the door during the cycle. It won't harm anything.
If you're curious to see a dishwasher in action, some appliance showrooms have a display model, where the spray parts and the racks are in an entirely transparent box. They're to show how powerfully and completely the stuff inside will get cleaned, but you can also see how the dishwasher is intended to work, by filling with just a couple of inches of water, and then recirculating it for the duration of the cycle, to loosen the stuff on the dishes.
It really is hard to say because there are many slots and we do not know what your teacher is teaching. I have seen a lot of teachers teaching out of date material. With that said, here is a list from best to worst.
PCI Express x16
PCI Express x1
AGP
PCI
This is list is based on greatest to least and base on the bandwidth read and write speed.
Revising and editing because it makes the report look sharp and business like.
<span>Use a dark color with light-color text to contrast the headers with the data.</span>
