In the following diagram bunsen flame the $\left(\mathrm{X}\right)$ represents.

Then A may have:

$\underset{(\mathrm{mixture} \mathrm{of} \mathrm{two} \mathrm{anions})}{\mathrm{A}}\underset{\mathrm{excess} \mathrm{of} {\mathrm{BaCl}}_2}{\overset{\mathrm{Cold}}{\to }}\mathrm{white} \mathrm{ppt}. \stackrel{\mathrm{filtered}}{\to }\left(\mathrm{filterate}\right)\stackrel{\mathrm{boil}}{\to }\mathrm{white} \mathrm{ppt}.\downarrow$

Anion of $\left(\mathrm{A}\right)$ could be: