Find out the major product from the following reaction.

If the radius of the first orbit of hydrogen atom is $$\alpha_{0}$$, then de Broglie's wavelength of electron in $$3^{\text {rd }}$$ orbit is :

Which one of the following elements will remain as liquid inside pure boiling water?

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

Assertion A : In the complex $$\mathrm{Ni}(\mathrm{CO})_{4}$$ and $$\mathrm{Fe}(\mathrm{CO})_{5}$$, the metals have zero oxidation state.

Reason R : Low oxidation states are found when a complex has ligands capable of $$\pi$$-donor character in addition to the $\sigma$-bonding.

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