# Which acid is manufactured by Ostwald's process

$\begin{array}{1 1}(a)\;Phosphoric\;acid&(b)\;Nitric\;acid\\(c)\;Carbonic\;acid&(d)\;Sulphuric\;acid\end{array}$

$4NO_2(g)+O_2(g)+2H_2O\rightarrow 4HNO_3$
(Ostwald's final step)
Hence (b) is the correct answer.