Consider the reaction sequence given below:
Which of the following statements is true?

Arrange the following labelled hydrogens in decreasing order of acidity :

The major product obtained from E₂ - elimination of 3-bromo-2-fluoropentane is

Three elements X, Y and Z are in the 3^rd period of the periodic table. The oxides of X, Y and Z, respectively, are basic, amphoteric and acidic. The correct order of the atomic numbers of X, Y and Z is :