A salt was being preared by adding an acid to a carbonate. However, after a while, the reaction ceased and a precipitate began to form without all of the carbonate reacting. Which of the following pairs of acids and carbonate could have been present?
A) CaCO3 H2SO4
B) CuCO HCl
C) BaCO3 HNO3
D) Na2CO3 H2SO4