One of the most resistant biological material present in the exine of pollen grain is

Options

A. pectocellulose
B. sporopollenin
C. suberin
D. cellulose

Explanation

**Step-by-Step Solution:**

1. **Understanding Pollen Grain Structure**: Pollen grains consist of two main layers: the outer layer called the exine and the inner layer known as the intine.

2. **Identifying the Composition of Exine**: The exine is the outer protective layer of the pollen grain. It is known for its toughness and resistance to environmental factors.

3. **Recognizing the Key Component**: The primary component of the exine is a substance known as sporopollenin. This is a complex biopolymer that provides the exine with its resistance.

4. **Comparing Other Components**: While the intine (the inner layer) is primarily made of cellulose, it is the sporopollenin in the exine that is recognized as one of the most resistant biological materials.

5. **Conclusion**: Therefore, the most resistant biological material present in the exine of pollen grain is sporopollenin.

**Final Answer**: Sporopollenin

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