To determine which galvanic cell corresponds to the given reaction:

$$\frac{1}{2} \mathrm{H}_{2(\mathrm{~g})}+\mathrm{AgCl}_{(\mathrm{s})} \rightarrow \mathrm{H}_{(\mathrm{aq})}^{+}+\mathrm{Cl}_{(\mathrm{aq})}^{-}+\mathrm{Ag}_{(\mathrm{s})}$$

we need to examine the setups of the given cells and check if they produce the same reactants and products as in the above reaction.

Analyzing the reaction, we observe:

• Hydrogen gas ($$\mathrm{H}_{2(\mathrm{~g})}$$) is involved at one electrode and splits into $$\mathrm{H}_{(\mathrm{aq})}^{+}$$ ions.
• Solid silver chloride ($$\mathrm{AgCl}_{(\mathrm{s})}$$) decomposes at another electrode into $$\mathrm{Ag}_{(\mathrm{s})}$$ and $$\mathrm{Cl}_{(\mathrm{aq})}^{-}$$ ions.

Let's examine each option:

Option A:

$$\mathrm{Pt}\left|\mathrm{H}_{2(\mathrm{~g})}\right| \mathrm{HCl}_{(\text {soln.) }}\left|\mathrm{AgNO}_{3(\mathrm{aq})}\right| \mathrm{Ag}$$

This cell setup does not directly involve $$\mathrm{AgCl}_{(\mathrm{s})}$$ solid separating into $$\mathrm{Ag}_{(\mathrm{s})}$$ and $$\mathrm{Cl}_{(\mathrm{aq})}^{-}$$. Hence, it does not match the reaction given.

Option B:

$$\mathrm{Ag}\left|\mathrm{AgCl}_{(\mathrm{s})}\right| \mathrm{KCl}_{(\text {(soln.) }}\left|\mathrm{AgNO}_{3 \text { (aq.) }}\right| \mathrm{Ag}$$

This involves silver electrodes and does not have a setup for reaction with hydrogen gas or the splitting of $$\mathrm{H}_{2(\mathrm{~g})}$$ into $$\mathrm{H}_{(\mathrm{aq})}^{+}$$ ions. So, this does not match either.

Option C:

$$\mathrm{Pt}\left|\mathrm{H}_{2(\mathrm{~g})}\right| \mathrm{KCl}_{(\text {soln.) }}\left|\mathrm{AgCl}_{(\mathrm{s})}\right| \mathrm{Ag}$$

While this configuration includes $$\mathrm{AgCl}_{(\mathrm{s})}$$ and $$\mathrm{H}_{2(\mathrm{~g})}$$, it uses potassium chloride solution instead of hydrochloric acid solution, which alters the chemistry and does not perfectly match the required reaction mechanism.

Option D:

$$\mathrm{Pt}\left|\mathrm{H}_{2(\mathrm{~g})}\right| \mathrm{HCl}_{(\text {soln. })}\left|\mathrm{AgCl}_{(\mathrm{s})}\right| \mathrm{Ag}$$

This configuration fits the reaction given. Here hydrogen gas at the platinum electrode splits into $$\mathrm{H}_{(\mathrm{aq})}^{+}$$ ions in the hydrochloric acid solution. On the other side, the solid silver chloride separates into $$\mathrm{Ag}_{(\mathrm{s})}$$ and $$\mathrm{Cl}_{(\mathrm{aq})}^{-}$$ ions. Hence, this accurately matches the reaction.

Therefore, the correct answer is:

Option D