Functions and clinical associations of biomolecules:

• Vitamin A (Retinol) deficiency leads to hardening of the cornea called Xerophthalmia and night blindness $\rightarrow$ (II)
• Thiamine (Vitamin $\text{B}_1$) deficiency causes Beri-Beri $\rightarrow$ (III)
• Glucocorticoids regulate carbohydrate metabolism; hyposecretion of adrenal cortex hormones causes Addison's disease $\rightarrow$ (IV)
• Estradiol is the primary female sex hormone that controls the development of secondary sexual characteristics and regulates the menstrual cycle $\rightarrow$ (I)

Correct match: (A)-(II), (B)-(III), (C)-(IV), (D)-(I).

Analysis of stereochemical statements:

• $\text{S}_\text{N}2$ reactions proceed via backside attack, leading to complete inversion of configuration (Walden inversion) $\rightarrow$ Statement A is correct.
• Racemisation is the conversion of an optically active enantiomer into an equimolar racemic modification, not the reverse (resolution is the separation of racemic mixtures into enantiomers) $\rightarrow$ Statement B is false.
• mixture containing two enantiomers in equal proportions is optically inactive due to external compensation and is called a racemic mixture $\rightarrow$ Statement C is correct.
• Enantiomers are non-superimposable mirror images, not superimposable $\rightarrow$ Statement D is false.
• Molecules or objects that cannot be superimposed on their mirror images are termed chiral, and this property is chirality $\rightarrow$ Statement E is correct.