Adsorption is multilayer in case of

The given graphs $I$,$II$,and $III$ represent general trends observed for different physisorption and chemisorption processes under mild conditions of temperature and pressure. Which of the following statements are correct?

The colloidal sol of $SnCl_4$ prefers the adsorption of which ion in the presence of excess $HCl$?

Sticking of one substance at the surface of another is called:

Why is chemisorption referred to as activated adsorption?

If the adsorbate is held on a surface by weak Van der Waals forces,the adsorption process is called: