The correct answer is option 3, which states that statements 2 and 3 are correct regarding recycling.

Option 1 states that recycling is just the collection and separation of waste materials. This statement is incorrect because recycling goes beyond just collecting and separating waste materials. It also involves processing those materials to produce marketable products.

Option 2 states that recycling is the collection and separation of materials from the waste stream and their subsequent processing to produce a marketable product. This statement is correct because it accurately describes the process of recycling. It highlights that recycling involves collecting and separating materials from the waste stream and then processing those materials to create new products that can be sold in the marketplace.

Option 3 states that recycling leads to a reduction in waste disposal costs. This statement is also correct because recycling decreases the amount of waste that needs to be disposed of, which can result in cost savings for waste management.

In summary, option 3 is the correct answer to the question as it accurately states that statements 2 and 3 are correct regarding recycling.