Species having X−O−H linkage ( X = non-metal with positive oxidation state) are called oxy acids and parent acid of a non-metal may exist in two form (a) -ic form of parent oxy acid (b) -us form of parent oxy acid.
Which of the following parent oxy acid does not have its pyro-oxy acid ?
a. H2SO3
b. HNO3
c. H3PO3
d. H4SiO4