Urea-forming ornithine cycle operates in liver/kidneys.

Explanation

### Step-by-Step Solution:

1. **Understanding the Ornithine Cycle**: The ornithine cycle, also known as the urea cycle, is a series of biochemical reactions that convert ammonia, which is toxic, into urea, which is less harmful and can be excreted from the body.

2. **Location of the Cycle**: The ornithine cycle primarily takes place in the liver. The liver cells, known as hepatocytes, are responsible for the conversion of ammonia into urea.

3. **Process of Urea Formation**: In the liver, ammonia is combined with carbon dioxide and other molecules through a series of enzymatic reactions to form urea. This process is crucial for detoxifying ammonia, which is a byproduct of protein metabolism.

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