Which of the following is a resistant survival stage of late blight of potato?

The correct answer is oospores, as this is the resistant survival stage of the late blight pathogen, Phytophthora infestans. Oospores are thick-walled, dormant structures formed through sexual reproduction and can withstand adverse conditions, allowing the pathogen to survive in the environment during periods when the host plants are not present, such as winter or during dry seasons.

Plant debris, while it can harbor pathogens, is not a defined survival stage specific to late blight. Zoospores are motile and responsible for the initial infection but do not have a persistent survival capability like oospores. Sclerotia are survival structures formed by some fungi, but they are not associated with Phytophthora infestans and thus are not relevant to late blight survival.