Electron transport is absent in fermentation / aerobic respiration.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Processes**: Start by recognizing the two processes in question: fermentation and aerobic respiration. Fermentation is an anaerobic process, meaning it occurs without oxygen, while aerobic respiration requires oxygen.

2. **Electron Transport Chain (ETC)**: The electron transport chain is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions. This process is crucial for ATP production in aerobic respiration.

3. **Fermentation Process**: In fermentation, glucose is broken down without the use of oxygen. The end products of fermentation can include ethanol and carbon dioxide, but importantly, this process does not involve the electron transport chain.

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