Digestion refers to the process where the food consumed by us is processed and broken down into smaller parts that can be absorbed by the body. Of all the parts of the digestive system, the connecting link from the mouth to the stomach is the oesophagus. It is a muscular tube that moves the partially digested food from mouth to the stomach for further digestion. Hence, the oesophagus is the part of the digestive system where no digestion occurs. Therefore, the correct answer is option B.