The correct answer is option 1, Algae. Chlorophyll-containing autotrophic thallophytes refer to organisms that can produce their own food through photosynthesis and have a thallus-like structure, such as algae. Algae are a diverse group of organisms that can be found in various aquatic habitats like oceans, lakes, and rivers, as well as on damp surfaces like rocks and tree trunks. They come in different shapes and sizes, ranging from microscopic unicellular species to large multicellular seaweeds. Algae contain chlorophyll, which allows them to capture sunlight and convert it into energy through photosynthesis. Therefore, the option "Algae" is the correct choice as it accurately describes chlorophyll-containing autotrophic thallophytes.