Consider the following statements regarding powder metallurgy:1) Refractory materials made of tungsten can be manufactured easily.2) In metal powder control of grain size results in relatively much uniform structure.3) The power heated in die or mould at high temperature is then pressed and compressed to get desired shape and strength.4) In sintering, the metal power is gradually heated resulting in coherent bond.Which of the above statements are correct?

• A. 1, 2 and 3 only
• B. 1, 2 and 4 only
• C. 2, 3 and 4 only
• D. 1, 2, 3 and 4