Q. In which organisms does spore formation occur as a mode of reproduction ?

The correct answer is: a) Fungi

Explanation: Spore formation is a common mode of reproduction in certain organisms, particularly in fungi. Fungi produce spores as a means of asexual reproduction. These spores are lightweight and can be dispersed easily through air, water, or other means. When they land in a suitable environment, they germinate and grow into new fungal organisms. While algae and ferns also produce spores, the question specifically focuses on spore formation as a mode of reproduction, which is most prominently associated with fungi. Yeast, on the other hand, primarily reproduces through budding rather than spore formation. Hence, the correct answer is fungi.