In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Let me give you an example: Question: A 13-year-old girl is operated on due to Hirschsprung illness at 3 months of age. Which of the following tumors is more likely to be present? 
 Options: <1> Abdominal neuroblastoma <2> Wilms tumor <3> Mesoblastic nephroma <4> Familial thyroid medullary carcinoma.
The answer to this example can be: 2
Here is why: The answer to the given question should be a tumor, therefore Wilms tumor is the correct answer for the given question.

OK. solve this:
Question: Which of the following substances is used as a catalyst in the Contact Process during the manufacture of sulfuric acid ?: 
 Options:  <1> RuO2. <2> V2O5 <3> Cr2O3. <4> RhO2. <5> PdO.
Answer:
2