• Cardinal Defects of Tetralogy of Fallot:
• Tetralogy of Fallot is a congenital malformation complex of the conotruncal septum consisting of four interrelated structural cardiac defects:
• Ventricular Septal Defect (VSD): Subaortic interventricular communication [TRUE].
• Pulmonary Stenosis: Hypoplastic pulmonary trunk or subpulmonic/infundibular narrowing obstructing right ventricular outflow [TRUE].
• Dextroposition (Overriding) of Aorta: The aortic root is shifted rightward directly above the VSD [TRUE].
• Hypertrophy of Right Ventricle: Secondary compensatory right ventricular myocardial hypertrophy due to systemic pressure overload (Statement B erroneously specifies left ventricular hypertrophy) [Statement B is FALSE].

Correct option: (4) (A), (C) and (D) only.

• Matching Morphological Patterns of Inflammatory Exudates:
• Serous inflammation $\longrightarrow$ (III) Fluid exudate low in protein and cell content: Characterized by transudate-like, clear fluid derived from plasma or mesothelial secretions (e.g., in skin blisters or early burn lesions).
• Fibrinous inflammation $\longrightarrow$ (I) Exudate rich in fibrinogen that polymerizes into fibrin networks: Typical of serous membrane surfaces (pericardium, pleura, peritoneum) showing bread-and-butter gross appearance.
• Purulent (Suppurative) inflammation $\longrightarrow$ (IV) Exudate prominent in neutrophils, liquefactive necrosis, and cellular debris: Typical of pyogenic bacterial infections resulting in pus formation (abscess).
• Catarrhal inflammation $\longrightarrow$ (II) Hypersecretion of mucus from epithelial surfaces: Occurs in mucous membranes of the respiratory and gastrointestinal tracts.
• Conclusion: (A) - (III), (B) - (I), (C) - (IV), (D) - (II) (Option 3).

Correct option: (3) (A) - (III), (B) - (), (C) - (IV), (B) - (I)

• Sub-Clinical Form of Infectious Bursal Disease (IBD):
• Age Window: The sub-clinical form occurs when susceptible chicks are infected early in life (below 3 weeks of age), typically during the first 1–2 weeks when maternally derived antibodies decline below protective thresholds.
• Pathological Hallmark: Characterized by massive cytolytic destruction of proliferating immature IgM+ B lymphocytes within the medullary follicles of the bursa of Fabricius, leading to severe, irreversible bursal atrophy and permanent, profound humoral immunosuppression without the acute inflammatory spike, spiking fever, or high mortality seen in birds infected after 3 weeks of age.
• Economic Impact: Results in poor vaccine responses, stunted growth, and devastating secondary bacterial infections (E. coli, gangrenous dermatitis).

Correct option: (3) It is characterized by destruction of immature B lymphocytes and atrophy of bursa.