_____________ are the dead cells of phloem.

Explanation

**Step-by-Step Solution:**

1. **Understanding Phloem**: Phloem is a type of vascular tissue in plants responsible for the transport of nutrients, particularly the products of photosynthesis (like sugars) from the leaves to other parts of the plant.

2. **Components of Phloem**: Phloem is made up of several types of cells, including sieve tubes, companion cells, phloem fibers, and phloem parenchyma. Each of these components has a specific function.

3. **Identifying Dead Cells**: Among these components, we need to identify which ones are dead cells. In phloem, the dead cells are specifically known as phloem fibers.

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