Given below are two statements :

Statement I : The halogen that makes longest bond with hydrogen in HX, has the smallest covalent radius in its group.

Statement II : A group 15 element's hydride $\mathrm{EH}_3$ has the lowest boiling point among corresponding hydrides of other group 15 elements. The maximum covalency of that element E is 4 .

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

The energy required by electrons, present in the first Bohr orbit of hydrogen atom to be excited to second Bohr orbit is $\_\_\_\_$ $\mathrm{J} \mathrm{mol}^{-1}$.

Given: $R_H=2.18 \times 10^{-11} \mathrm{ergs}$.

The correct order of the rate of reaction of the following reactants with nucleophile by $\mathrm{S}_{\mathrm{N}} 1$ mechanism is :

(Given : Structures I and II are rigid)

Consider the transition metal ions $\mathrm{Mn}^{3+}, \mathrm{Cr}^{3+}, \mathrm{Fe}^{3+}$ and $\mathrm{Co}^{3+}$ and all form low spin octahedral complexes. The correct decreasing order of unpaired electrons in their respective d-orbitals of the complexes is