Three main chemical constituents of wood are

Explanation:

The three main chemical constituents of wood are cellulose, hemi-cellulose, and lignin. Their typical proportions are as follows:

1. Cellulose (40% - 50%):

   • Cellulose is a polysaccharide consisting of a linear chain of glucose molecules. It provides strength and rigidity to the cell walls of wood. It is the primary structural component and the most abundant organic polymer in wood.

2. Hemi-cellulose (20% - 35%):

   • Hemi-cellulose is a heterogeneous group of polysaccharides that surround the cellulose fibers. It acts as a matrix that holds cellulose fibers together. Hemi-cellulose has a lower degree of polymerization and is more amorphous than cellulose, making it more easily hydrolyzed.

3. Lignin (15% - 35%):

   • Lignin is a complex organic polymer with a phenyl group structure that acts as a binder for cellulose fibers, providing rigidity and resistance to decay. It is hydrophobic, which makes it crucial for the water conduction properties of wood.

Option 1 provides the correct approximate percentage ranges of these three main constituents, making it the most accurate representation of the chemical composition of wood.