The correct answer is C - sound.
Sound is a wave, and it is thus not considered a form of matter.
Answer and Explanation:
(a)
: its chemical name is sodium sulfate in which sodium is present as
and sulfate is present as 
(b)
: Its chemical name is copper nitrate which is a inorganic compound which is mostly crystalline in nature
(c)
: Its chemical name is iron carbonate or ferric carbonate
(ANS1)— P4 + 5O2 ---> 2P2O5
(ANS2)— C3H8 + 5O2---> 3CO2 + 4H20
(ANS3)— Ca2Si + 4Cl2 ---> 2CaCl2 + SiCl4