$(a)$ Draw a diagram of the human alimentary canal and label the following: Oesophagus,Gall bladder,Liver,and Pancreas.
$(b)$ Explain the statement: 'Bile does not contain any enzyme but it is essential for digestion.'

(N/A) Refer to the provided diagram of the human alimentary canal.
$(b)$ Bile does not contain any digestive enzymes,yet it is essential for digestion due to the following reasons:
$(i)$ It makes the acidic food coming from the stomach alkaline,which is necessary for the action of pancreatic enzymes.
$(ii)$ It contains bile salts that help in the emulsification of fats,breaking down large fat globules into smaller ones to increase the efficiency of enzyme action.