Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : $$\mathrm{NH}_3$$ and $$\mathrm{NF}_3$$ molecule have pyramidal shape with a lone pair of electrons on nitrogen atom. The resultant dipole moment of $$\mathrm{NH}_3$$ is greater than that of $$\mathrm{NF}_3$$.

Reason (R) : In $$\mathrm{NH}_3$$, the orbital dipole due to lone pair is in the same direction as the resultant dipole moment of the $$\mathrm{N}-\mathrm{H}$$ bonds. $$\mathrm{F}$$ is the most electronegative element.

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

Number of $$\sigma$$ and $$\pi$$ bonds present in ethylene molecule is respectively :

The correct statement/s about Hydrogen bonding is/are

A. Hydrogen bonding exists when H is covalently bonded to the highly electro negative atom.

B. Intermolecular H bonding is present in $$o$$-nitro phenol

C. Intramolecular $$\mathrm{H}$$ bonding is present in HF.

D. The magnitude of $$\mathrm{H}$$ bonding depends on the physical state of the compound.

E. H-bonding has powerful effect on the structure and properties of compounds

Choose the correct answer from the options given below:

The number of species from the following that have pyramidal geometry around the central atom is _________

$$\mathrm{S}_2 \mathrm{O}_3^{2-}, \mathrm{SO}_4^{2-}, \mathrm{SO}_3^{2-}, \mathrm{S}_2 \mathrm{O}_7^{2-}$$