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

Assertion A : Hydrogen is the most abundant element in the Universe, but it is not the most abundant gas in the troposphere.

Reason R : Hydrogen is the lightest element.

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

Given below are two statements :

Statement I : The value of the parameter "Biochemical Oxygen Demand (BOD)" is important for survival of aquatic life.

Statement II : The optimum value of BOD is 6.5 ppm.

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

Which one of the following compounds is non-aromatic?

According to Bohr's atomic theory :

(A) Kinetic energy of electron is $$ \propto {{{Z^2}} \over {{n^2}}}$$.

(B) The product of velocity (v) of electron and principal quantum number (n), $$'vn' \propto {Z^2}$$.

(C) Frequency of revolution of electron in an orbit is $$ \propto {{{Z^3}} \over {{n^3}}}$$.

(D) Coulombic force of attraction on the electron is $$ \propto {{{Z^3}} \over {{n^4}}}$$.

Choose the most appropriate answer from the options given below :