Final answer:
Bill Gates co-founded Microsoft, which is the correct answer to the provided options. However, there isn't a specific cost associated with founding the company, as the business started as a startup and grew over time.
Step-by-step explanation:
The correct answer to what Bill Gates owns is: a) Microsoft, $1 billion. Bill Gates is a co-founder of Microsoft, which is one of the world's largest technology companies. He originally founded Microsoft with Paul Allen, and the company made its fortune through the development of software for personal computers, notably the Microsoft Windows operating system.
As for the cost associated with founding Microsoft, it did not involve a simple purchase transaction with a clear-cut figure like the options specified in the question. Instead, Microsoft started as a small software startup that grew to be a corporate giant thanks to the products and services it offered. Over time, the value of Microsoft increased significantly, and it would be misleading to imply that Gates 'bought' Microsoft for a specific sum like $1 billion as the company's value comes from its market capitalization which fluctuates.
Therefore, none of the options are factually correct when it comes to the bill or cost of founding Microsoft. The comparison to Apple and Steve Jobs pertains to Jobs co-founding Apple, which is separate from Bill Gates' business ventures.