i) ‘a’ is a physical change
ii) process ‘d’ is called condensation
iii) Process ‘b’ is a chemical change
iv) All Ice, water and water vapour are made up of  molecules only.

i) Process a is physical change (solid to liquid)
ii) Process d is condensation (water vapour to water)
iii) Process b is also physical change (liquid to solid)
iv) All ice, water and water vapour are made up of H₂O molecules only.