Anomalous behavior of oxygen is due to its

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

Assertion A : The first ionisation enthalpy decreases across a period.

Reason $$\mathbf{R}$$ : The increasing nuclear charge outweighs the shielding across the period.

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

Given below are two statements :

Statement I : The electronegativity of group 14 elements from $$\mathrm{Si}$$ to $$\mathrm{Pb}$$, gradually decreases.

Statement II : Group 14 contains non-metallic, metallic, as well as metalloid elements.

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

Given below are two statements :

Statement (I) : The $$4 \mathrm{f}$$ and $$5 \mathrm{f}$$ - series of elements are placed separately in the Periodic table to preserve the principle of classification.

Statement (II) : S-block elements can be found in pure form in nature.

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