The efficiency of a catalyst depends on which of the following?

Which one of the following is an example of homogeneous catalysis?

Which one of the following reactions is an example of heterogeneous catalysis?

Platinised asbestos helps in the formation of $SO_3$ from $SO_2$ and $O_2$. But,if even a small amount of $As_2O_3$ is present,the platinised asbestos does not help in the formation of $SO_3$. $As_2O_3$ acts here as

Formation of ammonia from $H_2$ and $N_2$ by Haber's process using $Fe$ is an example of

Which one of the following statements is not correct?