Observe the relationship between the first two words and then fill in the suitable word at the fourth place.
Nucleus : controlling centre of the cell : : nucleolus : __________

Explanation

To solve the analogy presented in the question, we need to identify the relationship between the first two terms: "Nucleus" and "controlling centre of the cell."

1. **Identify the relationship**: The nucleus is described as the controlling center of the cell. This means that it plays a crucial role in regulating cell activities and contains genetic material.

2. **Find the corresponding term**: Now, we need to find a similar relationship for "nucleolus." The nucleolus is a structure found within the nucleus.

3. **Understand the function of the nucleolus**: The primary function of the nucleolus is to produce ribosomes, which are essential for protein synthesis in the cell. It can be referred to as the "ribosomal factory" because it assembles ribosomal RNA (rRNA) and combines it with proteins to form ribosomes.

...