Cyanobacteria: ________ : : Paramoecium : Heterotrophs.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question presents a relationship between two organisms: Cyanobacteria and an unknown term, similar to how Paramecium relates to Heterotrophs.

2. **Identifying Paramecium's Nutrition**: Paramecium is known to be a heterotrophic organism. This means it cannot produce its own food and relies on other organisms for nutrition.

3. **Understanding Cyanobacteria**: Cyanobacteria are a type of bacteria that can perform photosynthesis and are classified as autotrophic organisms. This means they can produce their own food.

...