Consider following reactions :(i) $H_2(g)+I_2(g)\rightarrow 2HI(g),(ii)\;2Mg(s)+O_2(g)\rightarrow 2MgO(s),(iii)\;CaCO_3(s)+2H^+(aq)\rightarrow Ca^{+2}(aq)+H_2O(l)+CO_2(g)$.When we increase surface area will increase reaction rate in

$\begin{array}{1 1}(a)\;(ii)\;only&(b)\;(ii)\;and\;(iii)\;only\\(c)\;(i),(iii)\;only&(d)\;(i),(ii),(iii)\end{array}$

(i) reaction occurs purely in gaseous phase while (ii) & (iii) includes surface reactions.If we increase surface area in (ii) & (iii) then more no of molecules interacts and rate increases.
Hence (b) is the correct answer.