How many monosaccharide units make up the carbohydrate chains on the cell surface?

1. Carbohydrates are the third major component of plasma membranes and always sit on the exterior surface. 2. Their chains may consist of 2 to 60 monosaccharide units. 3. These chains can be either straight or branched, so any option forcing one shape is wrong on that count alone. 4. The figure of 20 to 25 belongs to the amino acids of a transmembrane protein segment, which is the trap here. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 5 "Structure and Function of Plasma Membranes", section 5.1 Components and Structure_