• Types of Microbial Interspecies Interactions:
• Pair-by-Pair Matching:
• Tetrahymena and Klebsiella $\rightarrow$ (II) Predation: Ciliated protozoan Tetrahymena acts as an active predator grazing on bacterial prey Klebsiella.
• Desulfovibrio and Methanobacterium $\rightarrow$ (V) Commensalism / Syntrophism: Often involved in interspecies metabolic transfers; here paired with (V).
• Enterococcus faecalis and E. coli $\rightarrow$ (IV) Syntrophism: Cross-feeding and mutual assistance in metabolic degradation pathways.
• Bdellovibrio and E. coli $\rightarrow$ (I) Parasitism / Predation: Bdellovibrio bacteriovorus is an obligate intraperiplasmic parasite/predator of Gram-negative bacteria like E. coli.
• Paramecium and Chlorella $\rightarrow$ (III) Mutualism: Endosymbiotic relationship where the alga Chlorella lives inside Paramecium bursaria, providing photosynthetic sugars while receiving nitrogenous waste and mobility.
• Correct Choice: Option 3 maps (A)-(II), (B)-(V), (C)-(IV), (D)-(I), (E)-(III).

Correct option: (3) (A) — (I), (B) - (VY), (C) - (IV), (D) = (1), (E) = (I)