Explanation:

Let's look at each statement with respect to the Inter-State Migrant Workmen (Regulation of Employment and Conditions of Service) Act, 1979:

- Equal pay for equal work irrespective of sex: The Act ensures equality in pay for inter-state migrant workers.

- Provision for suitable residential accommodation: Contractors must provide suitable residential accommodation.

- Provision for protective clothing: The Act mandates protective clothing when required by work conditions.

- Provision for old age benefit scheme: Not specifically required under the Act.

- Prescribed medical facilities: The Act requires contractors to provide prescribed medical facilities to workers.

Now, let's check your chosen option:

- Option: 1, 2, 3 and 5 only