Final answer:
Protists include both heterotrophs, which consume other organisms or organic material, and autotrophs, which produce their own food through photosynthesis. Additionally, some protists can be saprobes or mixotrophs, shifting between heterotrophic and autotrophic nutrition.
Step-by-step explanation:
The kingdom of protists is very diverse, including organisms with various nutritional strategies. Protists include both heterotrophs and autotrophs. Heterotrophs are organisms that obtain energy by consuming other organisms, while autotrophs make their own food. Examples of heterotrophic protists are those that consume other microorganisms or organic material. Subtypes such as saprobes absorb nutrients from dead organisms or their organic wastes.
In contrast, autotrophic protists, like plant-like ones including algae, kelp, and seaweed, can photosynthesize to produce their own food. They convert carbon dioxide and water into carbohydrates through photosynthesis. Some protists are even capable of mixotrophy, meaning they can switch between autotrophic and heterotrophic nutrition depending on environmental conditions. Therefore, the correct answer to the question is 'both a and b,' and protists that absorb nutrients from dead organisms are known as saprobes.