Both white phosphorous as well as red phosphorous

ANS:B - burns when heated in air.

Both white phosphorus and red phosphorus exhibit the following characteristics:

1. Solubility in CS2 (Carbon disulfide): Both white phosphorus and red phosphorus are soluble in CS2. This solubility is a characteristic property of phosphorus compounds.
2. Burning when Heated in Air: Both white phosphorus and red phosphorus are pyrophoric, meaning they spontaneously ignite in air when heated to a sufficiently high temperature. This property is due to their reactivity with oxygen in the air, resulting in combustion.
3. Reaction with Hot Caustic Soda Solution to Give Phosphine: Both white phosphorus and red phosphorus react with hot caustic soda solution (sodium hydroxide, NaOH) to produce phosphine gas (PH3) as a by-product. This reaction is a classic laboratory method for the preparation of phosphine.