Which one of the following compounds will liberate CO₂, when treated with NaHCO₃ ?

In the leaching of alumina from bauxite, the ore expected to leach out in the process by reacting with NaOH is :

An organic compound 'A' C₄H₈ on treatment with KMnO₄/H⁺ yields compound 'B' C₃H₆O.

Compound 'A' also yields compound 'B' an ozonolysis. Compound 'A' is :

The number of sigma bonds in


is _______________.