Answer:
Viscosity may be defined as the property of the liquids mainly that resist the movement of the liquid. Viscosity increases the thickness and shows the frictional force that exist between the fluid layers.
Propanol and glycol both have the alcohol as the functional force. But the ethylene glycol has two OH groups. This increase the viscosity because the hydrogen bonding will increase in this case. The hydrogen bonding increases the intermolecular force of attraction and molecule unable to move easily. This increases the viscosity.