Why don’t people eat things with very high levels of cellulose?

people cannot digest cellulose.
foods high in cellulose are expensive.
foods with high levels of cellulose are difficult to find.
cellulose is only food for cells.

People do not consume food that are high in cellulose content because we do not have the appropriate enzymes that will aid in properly digesting this type of food. That being said, the answer to this item is the first choice, "People cannot digest cellulose". 

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey

The correct answer is b