To solve this problem, we need to understand the solubility and crystallization behavior of the salts in the presence of HCl.$\\$When HCl is passed through a solution containing $$CaCl$_2,$MgCl$_2,$ and NaCl$,$ the solubility of these salts is affected by the common ion effect.$\\$• $$NaCl:$\\$The solubility of NaCl is relatively low compared to the other chlorides.$\\$When HCl is added, the concentration of Cl$^-$ ions increases, which decreases the solubility of NaCl due to the common ion effect.$\\$Thus, NaCl is likely to crystallize out of the solution.$\\$• $$MgCl$_2: \\$MgCl$_2$ is more soluble in water than NaCl. However, the addition of HCl increases the Cl$^-$ ion concentration, which can also lead to a decrease in the solubility of MgCl$_2. \\$However, it is less likely to crystallize compared to NaCl.$\\$• $$CaCl$_2: \\$CaCl$_2$ is highly soluble in water, and the addition of HCl does not significantly affect its solubility.$\\$Therefore, it is unlikely to crystallize out of the solution.$\\$Based on the above analysis, the most likely compound to crystallize is NaCl.$\\$Therefore, the correct answer is Option 1: Only NaCl.