Final answer:
Fructose is the sweetest of the listed sugars, 1.7 times sweeter than sucrose. Sucrose is glucose + fructose, lactose is glucose + galactose, and maltose is glucose + glucose. The structural differences in these sugars cause their different sweetness levels.
Step-by-step explanation:
Out of the sugars listed; fructose, glucose, maltose, and galactose, fructose is the sweetest. This is based on relative sweetness, where fructose is known to be 1.7 times sweeter than sucrose (table sugar), which consists of glucose + fructose. Consequently, fructose, which is abundant in honey and sweet fruits, is the correct answer to the which sugar is the sweetest.
It is important to clarify some common disaccharide formations:
Sucrose (table sugar) is made up of glucose + fructose.
Lactose (milk sugar) is composed of glucose + galactose.
Maltose (malt sugar) consists of glucose + glucose.
Other sugars such as lactose and maltose have lower sweetness levels compared to fructose. Galactose, which is a component of lactose, is less sweet than both glucose and fructose. The specific structure and arrangement of functional groups in these sugars are what lead to their varying levels of sweetness.