Hydrogenation of vegetable oil in the presence of Raney Nickel is an example of what?

When acidified $KMnO_4$ is added to hot oxalic acid solution,the decolourization is slow in the beginning,but becomes very rapid after some time. This is because :

In a chemical reaction,a catalyst .......

Which of the following statements is incorrect regarding a catalyst?

In a chemical reaction,a catalyst . . . . .

Which of the following catalysts is commonly used during the production of ammonia by the Haber process?