Which of the following can not be broken down by any herbivores digestive system

Cellulose cannot be digested and broken down by herbivorous digestive system.

Herbivores feed on plant based food. The herbivores have a digestive system which is capable of digestion of plant materials. The plants have higher starch and fibre which are the main energy source in the diet. Some of the plant materials like cellulose are hard to digest. The digestive tract of herbivores is adapted such that plant food is digested properly. The herbivorous organisms lack enzymes for the digestion of the cellulose.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.