$\mathrm{HCl}$ was passed through a solution of ${\mathrm{CaCl}}_2$, ${\mathrm{MgCl}}_2$ and $\mathrm{NaCl}$. Which of the following compound(s) crystallise(s)?

• Correct answer
  A

  Only $\mathrm{NaCl}$
• B

  Only ${\mathrm{MgCl}}_2$
• C

  $\mathrm{NaCl},{\mathrm{MgCl}}_2$ and ${\mathrm{CaCl}}_2$
• D

  Both ${\mathrm{MgCl}}_2$ and ${\mathrm{CaCl}}_2$

Hence, the correct answer is option: 'A'.