If a drug is active against the preerythrocytic stage of the malarial parasite it will be useful as a

Correct Answer: B

Rationale: Preerythrocytic activity makes a drug a causal prophylactic, preventing initial liver-stage infection.

Correct Answer: C

Rationale: Mefloquine is recommended for chloroquine-resistant P. falciparum areas, not selective only to resistant strains.

Correct Answer: B

Rationale: Quinine is not used for malaria prophylaxis due to toxicity and short duration of action.

Correct Answer: B

Rationale: Primaquine targets pre- and exoerythrocytic stages (hypnozoites), more than erythrocytic stages.

Correct Answer: A

Rationale: Metronidazole is the drug of choice for amoebic dysentery and liver abscess, but not the most effective for cyst eradication.