The adsorbent used in adsorption chromatography is/are A. silica gel B. alumina C. quick lime D. magnesia Choose the most appropriate answer from the options given below :

To determine the correct adsorbent(s) used in adsorption chromatography, let us analyze the properties of the given substances:

1. Silica gel: Silica gel is a highly porous form of silicon dioxide (${\mathrm{SiO}}_2$). It contains polar silanol ($\mathrm{—Si—OH}$) groups on its surface, making it an excellent polar stationary phase (adsorbent) widely used in column chromatography and thin-layer chromatography (TLC) to separate compounds based on their polarities.
2. Alumina (Aluminum oxide, ${\mathrm{Al}}_2{O}_3$): Similar to silica gel, alumina is a polar active solid phase. It is another highly common adsorbent used in adsorption chromatography, particularly for separating relatively basic or neutral organic compounds.
3. Quick lime (Calcium oxide, $\mathrm{CaO}$): Quick lime is a basic oxide that reacts readily with moisture and carbon dioxide, and it is not typically employed as a standard adsorbent in chromatography.
4. Magnesia (Magnesium oxide, $\mathrm{MgO}$): While magnesia has basic properties and has limited specialized uses, it is not one of the primary or commonly designated standard adsorbents in general adsorption chromatography compared to silica gel and alumina.

Therefore, the most appropriate and widely recognized adsorbents used in adsorption chromatography are silica gel and alumina (A and B).

Thus, the correct option is A and B only.