Cellulose is referred as insoluble fiber on food packages. Insoluble fiber lacks solubility in water but have passive water-attracting properties that augment to increase bulk and moisture of the stool. The water-holding quality of cellulose shorten the transit time of food to pass through the stomach and intestinal tract. Moreover, cellulose is mostly made up from the structural component of cell walls in green plants and vegetables.
I believe the answer is 3.Cellulose
Fiber is carbohydrate that can't be digested by human. Consumption of fiber will not give calorie like other food do, but it has other benefit for the digestive system such as helping regulate blood sugar level and satiety.
Cellulose is fiber that could be found in cell wall of green plants. Cellulose is the most common insoluble fiber.
It's the tough matter found in whole grains, nuts, and fruits and veggies that doesn't dissolve in water.