The correct answer is: A. Phytoplanktons.
Phytoplanktons are microscopic organisms that are able to photosynthesize, meaning they can use sunlight to create their own food. They are a major part of the food chain in aquatic ecosystems, and they play a vital role in the production of oxygen.
Zooplanktons are also microscopic organisms, but they are not able to photosynthesize. They must consume other organisms in order to survive. Zooplanktons are an important food source for many larger animals, including fish, whales, and birds.
Both phytoplanktons and zooplanktons are important components of aquatic ecosystems. However, phytoplanktons are the only organisms that are able to photosynthesize. This means that they are the primary producers in aquatic ecosystems, and they play a vital role in the production of oxygen.
Here is a brief explanation of each option:
- Option A: Phytoplanktons are microscopic organisms that are able to photosynthesize. They are a major part of the food chain in aquatic ecosystems, and they play a vital role in the production of oxygen.
- Option B: Zooplanktons are also microscopic organisms, but they are not able to photosynthesize. They must consume other organisms in order to survive. Zooplanktons are an important food source for many larger animals, including fish, whales, and birds.
- Option C: Both phytoplanktons and zooplanktons are important components of aquatic ecosystems. However, phytoplanktons are the only organisms that are able to photosynthesize. This means that they are the primary producers in aquatic ecosystems, and they play a vital role in the production of oxygen.
- Option D: None of these options are correct.