Answer: D. KI(aq) and \(\text{AgNO}_3\)(aq) are both colourless aqueous solutions. When mixed: \(\text{Ag}^+\text{(aq)} + \text{I}^-\text{(aq)} \rightarrow \text{AgI}\text{(s)}\), a yellow precipitate of silver iodide. The spectator ions \(\text{K}^+\) and \(\text{NO}_3^-\) remain in colourless solution.
So the observation is: two colourless solutions react to give a yellow precipitate and a colourless solution — option D.
Options A and B wrongly claim one starting solution is yellow (both KI and \(\text{AgNO}_3\) are colourless before mixing). Option C describes a white precipitate and a yellow solution; neither matches AgI (which is yellow, not white) and the spectator solution is colourless, not yellow.
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