These questions test the students' familiarity of the basic CS topics taught during the previous year. It's a test on the subject matters of the CS courses. If you don't use some of these stuff over the years, you will forget about them. I forgot the properties of the bipartite graph and have to look them up.

This reminds me of those trigonometry proofs we learnt in high school. I remember I could go through those complicate trig proofs with ease back then. Now beside some basic sine/consine stuff due to work, I completely forgot about the rest of them since there wasn't a chance to use any of them.

Basic course level knowledge are good to learn. Just the test needs to be relevant and in context.