Match the compounds in LIST-I with the observation in LIST-II, and choose the correct option.

LIST-I	LIST-II
(I) Aniline	(P) Sodium fusion extract of the compound on boiling with FeSO$$_4$$, followed by acidification with conc. H$$_2$$SO$$_4$$, gives Prussian blue color.
(II) o-Cresol	(Q) Sodium fusion extract of the compound on treatment with sodium nitroprusside gives blood red color.
(III) Cysteine	(R) Addition of the compound to a saturated solution of NaHCO$$_3$$ results in effervescence.
(IV) Caprolactam	(S) The compound reacts with bromine water to give a white precipitate.
	(T) Treating the compound with neutral FeCl$$_3$$ solution produces violet color.

First recall the characteristic qualitative tests involved:

(i) Lassaigne (sodium-fusion) test for nitrogen - the fusion extract, on boiling with $$FeSO_4$$ and then acidifying with conc. $$H_2SO_4$$, gives a Prussian-blue colour due to formation of $$Fe_4[Fe(CN)_6]_3$$. (Observation P)

(ii) Sodium-fusion extract + sodium nitroprusside $$\rightarrow$$ blood-red colour when sulphide ion ($$S^{2-}$$) is present. (Observation Q)

(iii) Addition of the organic compound to a saturated $$NaHCO_3$$ solution - brisk effervescence (release of $$CO_2$$) is obtained only when the compound possesses an acidic $$-COOH$$ group. (Observation R)

(iv) Bromine water test - phenols and aromatic amines are rapidly brominated to give a white precipitate of the tribromo derivative. (Observation S)

(v) Neutral $$FeCl_3$$ test - phenolic $$-OH$$ groups form coloured complexes (violet, blue, green etc.). (Observation T)

Now examine each compound in LIST-I.

Case I: Aniline, $$C_6H_5NH_2$$
• Contains nitrogen ⇒ positive Lassaigne test ⇒ Observation P.
• Aromatic amine reacts instantaneously with bromine water to give 2,4,6-tribromoaniline (white ppt.) ⇒ Observation S.
Hence I $$\to$$ P, S.

Case II: o-Cresol (2-methylphenol)
• It is a phenol; neutral $$FeCl_3$$ gives a violet complex ⇒ Observation T.
• Although phenols also give a bromine-water test, the option set that satisfies all compounds uniquely associates o-cresol only with Observation T.
Hence II $$\to$$ T.

Case III: Cysteine, $$HSCH_2CH(NH_2)COOH$$
• Contains sulphur ⇒ sodium-fusion extract with sodium nitroprusside gives blood-red colour ⇒ Observation Q.
• Contains a carboxylic acid group; addition to $$NaHCO_3$$ liberates $$CO_2$$ gas ⇒ effervescence ⇒ Observation R.
Hence III $$\to$$ Q, R.

Case IV: Caprolactam (the lactam of 6-aminocaproic acid)
• Contains nitrogen but no sulphur or acidic $$-COOH$$ group. Therefore only the Prussian-blue Lassaigne test is positive ⇒ Observation P.
Hence IV $$\to$$ P.

Collecting all the matches:
I $$\to$$ P, S ; II $$\to$$ T ; III $$\to$$ Q, R ; IV $$\to$$ P

This correspondence is exactly the one given in Option D.

Therefore, the correct choice is:
Option D which is: I $$\to$$ P, S; II $$\to$$ T; III $$\to$$ Q, R; IV $$\to$$ P.