Which of the following is an example of adsorption? a$)$ Dissolving sugar in water $($Dissolution$,$ not adsorption$)$ b$)$ Boiling water $($Change of state, not adsorption$)$ c$)$ Sticking a stamp to an envelope $($Adsorption between solid and solid$)$ d$)$ Rusting of iron $($Chemical reaction, not adsorption$)??$