An unsaturated hydrocarbon X on ozonolysis gives A. Compound A when warmed with ammonical silver nitrate forms a bright silver mirror along the sides of the test tube. The unsaturated hydrocarbon X is :

The exact volumes of 1 M NaOH solution required to neutralise 50 mL of 1 M H₃PO₃ solution and 100 mL of 2 M H₃PO₂ solution, respectively, are :

The characteristics of elements X, Y and Z with atomic numbers, respectively, 33, 53 and 83 are :

Which of the following is least basic?