Given are the figures for two types of plastics:
 
Which of the following statements are correct about P and Q?
I.   P is a linear polymer whereas Q is a cross-linked polymer.
II.  P is plastic whereas Q is a polymer.
III. P is polymer and Q is plastic
IV.  A single square represents a monomer unit.
AI and II
BIII and IV
CI, II, III and IV
DIV only
option 2 is confusing