What part of the digestive system first causes chemical changes to food? A. teeth in the mouth
B. saliva in the mouth
C. enzymes in the stomach
D. enzymes in the small intestine

b. saliva in the mouth

Explanation:

saliva contains enzymes that help break down food

good thing- during decomposition the organic molecules in organic matter are broken down into simpler organic molecules that require further decomposition or into mineralised nutrients

bad thing- it can be harmful in crop productivity

answer:

sequence 1- deletion

                  2- duplication

                  3- insertion

                  4- substitute

                  5- inversion