Each lung is covered by pericardium/pleura.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which structure covers the lungs: pericardium or pleura.

2. **Defining Pericardium**: The pericardium is a double-walled sac that surrounds the heart. Its primary function is to provide mechanical protection to the heart and to lubricate it, reducing friction between the heart and surrounding structures.

3. **Defining Pleura**: The pleura is a thin membrane that covers the lungs. It consists of two layers: the visceral pleura (which is attached to the lungs) and the parietal pleura (which lines the chest wall). The pleura serves to protect the lungs and facilitate their movement during breathing.

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