Silica gel, finely divided nickel and metal surface all have a porous structure which makes them good adsorbent. Thus they facilitate the adsorption process.

Therefore, (i), (iii) and (iv) are wrong options.

Calcium chloride is a strong hygroscopic substance which absorbs moisture readily. Thus, water is easily absorbed by CaCl₂ making it good absorbent.

Therefore, (ii) is correct.