Study the diagram given below and then answer the questions that follow :
(a) Name the parts labelled 1, 2, 3, 4, 5 and 6.
(b) Identify the tooth and give a reason to support your answer.
(c) Describe the structure of the part labelled '3'.
(d) Give the total number of the type of tooth mentioned in 'l' above, in the mouth of an adult and state its function.