Which layer is responsible for earth's magnetic field? Why?

Look at the figure on the side and answer the questions:

(i) Label the parts: (1), (2), (3), (4) and (5).
(ii) Name the state (solid, liquid or gas) in which each part exists.
(iii) Which part of the earth is suitable for human habitation? Why?

Give a geographical reason for each of the following:

(i) Nife is so called.

(ii) The core of the earth is the most inaccessible part of the earth.

(iii) The earth's crust undergoes many changes.

State two chief characteristics of the earth's crust.