Which of the following reactions will lead to a redox reaction?

In which of the following redox reactions is a precipitate $NOT$ formed?

In which of the following reactions does $HNO_3$ $NOT$ act as an oxidizing agent?

Which of the following reactions represents a redox reaction involving water?

Consider the following list of reagents:
Acidified $K_2Cr_2O_7$,alkaline $KMnO_4$,$CuSO_4$,$H_2O_2$,$Cl_2$,$O_3$,$FeCl_3$,$HNO_3$ and $Na_2S_2O_3$. The total number of reagents that can oxidise aqueous iodide to iodine is

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$BaCO_3 \downarrow + 2CH_3COOH \longrightarrow Ba(CH_3COO)_2 + CO_2 \uparrow + H_2O$