Explanation

(b)
$Starch\ + \ iodine\ \rightarrow \ blue\ colour$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \overset{\ \ \ \ \ \mathrm{\Delta}\ \ \ \ \ }{\rightarrow}\ blue\ colour\ disappears$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \overset{\ \ \ \ \ Cool\ \ \ \ \ \ }{\rightarrow}\ blue\ colour\ reappears$
So, iodine test is given by starch.