Observe the relationship between the first two words and then fill in the suitable word at the fourth place.
Mitochondria : cristae : : chloroplast : ____________

Explanation

To solve the analogy "Mitochondria : cristae : : chloroplast : ____________", we need to analyze the relationship between the first two words.

1. **Identify the first two words**: The first word is "Mitochondria" and the second word is "cristae".
2. **Understand the relationship**: Mitochondria are organelles in cells that are responsible for producing energy. The cristae are the inner membrane folds of mitochondria that increase the surface area for chemical reactions involved in energy production.
3. **Identify the corresponding organelle**: The second pair involves "chloroplast", which is another type of organelle found in plant cells. Chloroplasts are responsible for photosynthesis.
4. **Determine the equivalent structure in chloroplasts**: Just as cristae are the folded structures in mitochondria, the equivalent structure in chloroplasts is "thylakoids". Thylakoids are the membrane-bound compartments inside chloroplasts where the light-dependent reactions of photosynthesis occur.
5. **Fill in the blank**: Therefore, the suitable word to fill in the blank is "thylakoids".

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