The correct answer is option 1: Cellulose.

Cellulose is the most important component for the paper industry. It is a complex carbohydrate found in plant cell walls and serves as the structural component of plants. Cellulose provides strength and stability to the plants, making it an essential material for the production of paper.

Option 2 - Lignin and secondary xylem: Lignin is another component found in plant cell walls, but it is not as crucial for the paper industry as cellulose. Lignin provides rigidity and waterproofing to plants, but it adds complexity and impurities to the paper-making process. Secondary xylem refers to the wood tissue in plants, which contains both cellulose and lignin.

Option 3 - Lignin only: This is incorrect because lignin alone is not sufficient for producing paper. Lignin has limited use in the paper industry due to its negative impact on the paper-making process.

Option 4 - Starch: Starch is a carbohydrate found in plants, but it is not a primary component used in the paper-making process. Starch is commonly used in other industries, such as food and textile, for its thickening and binding properties.

In summary, while lignin and