Given below are two statements: one is labelled as Assertion $$\mathbf{A}$$ and the other is labelled as Reason $$\mathbf{R}$$

Assertion A : $$3.1500 \mathrm{~g}$$ of hydrated oxalic acid dissolved in water to make $$250.0 \mathrm{~mL}$$ solution will result in $$0.1 \mathrm{~M}$$ oxalic acid solution.

Reason $$\mathbf{R}$$ : Molar mass of hydrated oxalic acid is $$126 \mathrm{~g} \mathrm{~mol}^{-1}$$

In the light of the above statements, choose the correct answer from the options given below.

The correct order of the number of unpaired electrons in the given complexes is

A. $$\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}$$

B. $$\left[\mathrm{Fe} \mathrm{F}_{6}\right]^{3-}$$

C. $$\left[\mathrm{CoF}_{6}\right]^{3-}$$

D. $$\left.[\mathrm{Cr} \text { (oxalate})_{3}\right]^{3-}$$

E. $$\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]$$

Choose the correct answer from the options given below:

The correct relationships between unit cell edge length '$$a$$' and radius of sphere '$$r$$' for face-centred and body-centred cubic structures respectively are :

Number of water molecules in washing soda and soda ash respectively are :