All pigments except `"_____________"` are called accessory pigments.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the pigment that is not classified as an accessory pigment.

2. **Definition of Accessory Pigments**: Accessory pigments are light-absorbing compounds found in photosynthetic organisms that assist in the process of photosynthesis. They work alongside chlorophyll a.

3. **Identifying Main Pigments**: The most important pigment in photosynthesis is chlorophyll a. It is the primary pigment responsible for capturing light energy.

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