Which of the following best explains how the structures of chitin and cellulose make them hard to digest? They both have an alternating arrangement of glucose molecules held together by hydrogen bonds, and both are insoluble.
They both have branching chains of glucose molecules, but cellulose can be digested and chitin cannot.
They both have an alternating arrangement of glucose molecules, but only chitin has the ability to store glucose.
They both have branching chains of glucose molecules, but only cellulose provides structure and support to the organism.

They both have an alternating arrangement of glucose molecules, but cellulose has hydrogen bonds while chitin has amino group bonds.

Explanation:

They both have an alternating arrangement of glucose molecules, but cellulose has hydrogen bonds while chitin has amino group bonds.  

Both cellulose and chitin are straight chain polymers of glucose. In cellulose, these chains are linked via beta linkage and in chitin, the hydroxyl group is replaced with an amino group.

Humans lack enzymes to break both, and thus unable to digest the same.

i believe it would be the lungs.

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs