Read the following statements and determine the incorrect one .

Options

A. When pollen is shed at two - celled stage single fertilization takes place
B. Vegetative cell is larger than generative cell
C. Pollen grains in some plants remain viable for months
D. Intine is made up of cellulose and pectin

Answer

To determine the incorrect statement from the provided options, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Understanding the Pollen Grain Development**:
- Pollen grains typically develop in two stages: the two-celled stage and the three-celled stage. In many flowering plants, the pollen is shed at the two-celled stage.

2. **Analyzing Statement 1**:
- The statement claims that when pollen is shed at the two-cell stage, single fertilization takes place. This is incorrect because in flowering plants, when pollen germinates, it usually leads to double fertilization, not single fertilization. Therefore, this statement is incorrect.

3. **Analyzing Statement 2**:
- The statement mentions that the vegetative cell is larger than the generative cell. This is a correct statement as the vegetative cell (which forms the pollen tube) is indeed larger than the generative cell (which divides to form sperm cells).

4. **Analyzing Statement 3**:
- The statement states that pollen grains in some plants remain viable for months. This is also correct, as certain pollen grains can remain viable for extended periods under suitable conditions.

5. **Analyzing Statement 4**:
- The statement discusses the structure of the pollen grain, specifying that the inner layer is called entine and the outer layer is called exine, with entine being made up of cellulose and pectin. This is a correct statement as well.

6. **Conclusion**:
- After analyzing all the statements, we conclude that the incorrect statement is the first one: "When pollen is shed at the two-cell stage, single fertilization takes place." The correct process involves double fertilization.

### Final Answer:
The incorrect statement is: "When pollen is shed at the two-cell stage, single fertilization takes place."