Amylose is a water-soluble part of starch. What is the percentage solubility of it?

The correct option is 15 to 20%.

Starch is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. It is the most common carbohydrate in human diets and is contained in large amounts in staple foods such as potatoes, wheat, maize (corn), rice, and cassava.

Naturally occurring starch is not a single uniform substance but is actually a mixture of two different polysaccharides: amylose and amylopectin.
1. Amylose: It is a linear, unbranched polymer of glucose units linked by $\alpha -1,4-$glycosidic bonds. Amylose is water-soluble and typically makes up about 15% to 20% of the total starch structure.
2. Amylopectin: It is a highly branched polymer of glucose units, where branching occurs via $\alpha -1,6-$glycosidic bonds along with the linear $\alpha -1,4-$glycosidic linkages. Amylopectin is insoluble in water and constitutes the remaining major portion of starch, which is approximately 80% to 85%.

Since amylose constitutes the water-soluble portion of starch, its percentage composition or solubility percentage in starch is 15 to 20%.