Which compound gives apple green colour in flame test?

The correct option is ${\mathrm{BaSO}}_4$.

Explanation:
A flame test is a qualitative analysis test used in chemistry to identify the presence of certain metal ions (cations) based on the characteristic color they emit when heated in a flame.
When a metal salt is heated in a Bunsen burner flame, the electrons in the metal ions absorb thermal energy and are excited to higher energy levels. When these electrons drop back down to their ground state, they release energy in the form of light of a specific wavelength (color).
Different metal ions produce characteristic colors in a flame test:
• Calcium (${\mathrm{Ca}}^{2+}$) ions impart a brick-red color to the flame.
• Barium (${\mathrm{Ba}}^{2+}$) ions impart a characteristic apple-green (pale green) color to the flame.
• Aluminium (${\mathrm{Al}}^{3+}$) and Manganese (${\mathrm{Mn}}^{2+}$) do not produce a distinct characteristic color in standard flame tests.
Therefore, among the given compounds, barium sulfate, ${\mathrm{BaSO}}_4$, contains barium ions (${\mathrm{Ba}}^{2+}$) which give an apple green color in the flame test.