Which of the following is autotrophic?

Algae is the autotrophic organism among the options provided. Algae are photosynthetic organisms containing chlorophyll, which enables them to convert sunlight into energy through photosynthesis. They utilize carbon dioxide and water to produce glucose and oxygen. In contrast, protozoa are heterotrophic, obtaining nutrients by ingesting organic matter. Fungi, although diverse in their nutritional strategies, are primarily heterotrophic, feeding on decaying organic material or living organisms. They absorb nutrients through their hyphae from their surroundings. Viruses, unlike living organisms, lack metabolic machinery and rely on host cells for replication. They cannot produce energy or synthesize organic molecules independently. Therefore, among the options given, only algae possess the ability to sustain themselves through autotrophic means, making them essential components of aquatic ecosystems and primary producers in many environments.