Which of the following is heat resistant organelle?

Explanation

Spores are the most heat-resistant structures formed by certain bacteria, allowing them to endure extreme environmental conditions, including high temperatures, radiation, and dehydration. This adaptation ensures bacterial survival until conditions become favorable again. In contrast, cysts provide protection against some unfavorable conditions but do not offer the same level of heat resistance as spores. Granules are used for nutrient storage and do not confer heat resistance. Therefore, option A is the correct choice, as only spores are specifically designed to be heat resistant.