What type of carbohydrate would you guess this to be?

A component of many foods you ear is "fiber", which is a carbohydrate. Humans cannot digest fiber. What type of carbohydrate would you guess this to be, and explain why? Why do we need fiber?|||It helps our intestines work more efficiently! Simply said, it helps removes waste from our bodies. It's put under carbphydrate, since fiber is in plants like cereals, radishes, lettuce, whole grains, etc..