Which of the following catalysts is used in the decomposition of $KClO_3$?

What is the role of a catalyst in a catalysed reaction?

Which of the following acts as a negative catalyst?

Iron $(III)$ catalyses the reaction between iodide and persulphate ions,in which
$A$. $Fe^{3+}$ oxidises the iodide ion
$B$. $Fe^{3+}$ oxidises the persulphate ion
$C$. $Fe^{2+}$ reduces the iodide ion
$D$. $Fe^{2+}$ reduces the persulphate ion
Choose the most appropriate answer from the options given below:

Hydrogenation of vegetable oils in the presence of finely divided $Ni$ as a catalyst. The reaction is:

What is the role of $MnO_2$ in the decomposition reaction $2KClO_3 \to 2KCl + 3O_2$?