To solve this problem, we need to understand why cellulose does not form a blue color with iodine. Let's analyze the options:$\newline \bullet$Option 1: It is a disaccharide.$\newline$ - Cellulose is not a disaccharide; it is a polysaccharide composed of glucose units linked by $\beta$-1,4-glycosidic bonds.$\newline$ - Therefore, this option is incorrect.$\newline \bullet$Option 2: It is a helical molecule.$\newline$ - Cellulose is not a helical molecule; it has a linear, fibrous structure.$\newline$ - This option is incorrect because cellulose does not have a helical structure.$\newline \bullet$Option 3: It does not contain complex helices and hence cannot hold iodine molecules.$\newline$ - This is correct. Cellulose's linear structure does not form the helical cavities needed to trap iodine molecules.$\newline$ - In contrast, amylose (a component of starch) forms a helical structure that can trap iodine, resulting in a blue color.$\newline \bullet$Option 4: It breaks down when iodine reacts with it.$\newline$ - This is incorrect. Cellulose does not break down upon reaction with iodine; it simply does not form a complex.$\newline$Therefore, the correct answer is Option 3: It does not contain complex helices and hence cannot hold iodine molecules.