Read the following statement and explanation and answer as per the options given below:

STATEMENT (S): In the titration of Na₂CO₃ with HCl using methyl orange indicator, the volume required at the equivalence point is twice that of the acid required using phenolphthalein indicator.

EXPLANATION (E): Two moles of HCl are required for the complete neutralization of one mole of Na₂CO₃

Arrange of the following in :
Increasing order of ionic size:
N^3-, Na⁺, F^-, O^2-, Mg²⁺

Arrange of the following in :
Increasing order of basic character
MgO, SrO, K₂O, NiO, Cs₂O

The linear structure is assumed by :