Carbon exhibits allotropy and occurs as
i) Diamond, a beautiful crystalline substance
ii) Graphite, a soft greyish black crystalline substance
iii) Amorphous carbon, black residue left when carbon compounds are heated.
Which of the following are true:
I. The crystal of diamond is very hard and has high melting and boiling points.
II. Diamond is the purest allotrope of carbon.
III. Diamonds are supposed to have been formed due to the crystallization of carbon from molten mass under a very high pressure.
IV. Diamond is used for cutting glass, marbles and for drilling rocks.