They all can provide you with information. They all require energy in some form. Teachers require energy by consuming food, and their bodies then convert that food into energy, and then burn that energy throughout every day tasks. Computers require electrical energy to operate. A book, this one is a bit of a stretch, requires energy because as you read that book, aside from the usual autonomous tasks your body performs such as blinking eyes and beating heart, your brain is constantly computing each word you read, and everything your body is doing, even when you simply turn the page, your body is constantly burning energy, which, like the teacher, is acquired through food. Another thing that's common among these objects is that they are all physical objects, otherwise known as concrete nouns. Concrete nouns are, well, a noun is a person, place, or thing, and a concrete noun is a person, place, or thing that is a physical object. So "California" is not a concrete noun, it's just a location. Yes you can technically touch California by touching the ground while being within the governmentally defined bounds of California, it's not quite the same as say, a computer, which you can actually physically touch a computer. A good way to remember this is to think of "concrete" it's a concrete noun, like a sidewalk. Another similarity between all these items is that they can all be found at a school. Computer in the computer lab, book in the library, and teacher in the classroom. Lastly, they all have some form of skin. The plastic casing on a computer acts as a skin, the cover on a book is like a skin, and well, I most certainly hope your teachers have skin, if they don't, please send pictures.