Out of 1.0 g dioxygen, 1.0 g (atomic) oxygen and 1.0 g of ozone, the maximum number of oxygen atoms are contained in -

8 g of O_(2) has the same number of oxygen atoms as

2 g of oxygen contain same number of atoms as contained by

2g of oxygen contains number of atoms equal to that in

In an experiment, 4g of M_(2)O_(x) oxide was reduced to 2.8g of the metal. If the atomic mass of the metal is 56g"mol"^(-1) , the number of oxygen atoms in the oxide is: