The correct answer is option 4: Sucrose. Sugarcane is grown primarily to obtain sucrose, which is a type of sugar. Sucrose is the main component of sugarcane and is extracted from the stalks. It is a disaccharide made up of glucose and fructose molecules.

To understand why the other options are not correct, let`s briefly explain them:

Option 1: Starch is a polysaccharide and is generally obtained from crops like maize, potatoes, and wheat. Sugarcane does not contain significant amounts of starch.

Option 2: Glucose is a monosaccharide and is a simple sugar that serves as a primary source of energy in living organisms. While glucose is present in sugarcane, it is not the main reason for cultivating the crop.

Option 3: Fructose is also a monosaccharide and is commonly found in fruits and honey. While it is present in small amounts in sugarcane, it is not the main reason for its cultivation.

Therefore, the correct answer remains option 4: Sucrose, as it is the primary sugar obtained from sugarcane.