A wet towel is hanging on a clothesline in the sun. What process does the towel dry by?

By convection radiation ... the heat from the sun travels to the towel through air molecules (radiation), the heat is then transfer in the towel through water molecules (convection) ... thereby gradually drying up the water molecules in the towel

The towel dries by the process of evaporation. The sun heats up the water and changes it to water vapour.