Most mechanical processing of food occurs in the most mechanical processing of food occurs in the oral cavity and stomach oral cavity and small intestine stomach and small intestine small intestine and large intestine

Oral cavity and stomach

Explanation:

Digestion is one of many different processes the human body carries out on a daily basis. The mechanical processing of food occurs in the oral cavity and stomach since it is there where the chewing process takes place, the teeth, tongue, and saliva help to break the food into smaller pieces, the rest of the process which is chemical starts later on.          

all the above is what i would say