Certain taxpayers are eligible for a deduction for Qualified Business Income (QBI). Which of the following taxpayers are eligible for the QBI deduction?

I.	A single taxpayer with taxable income of $100,000, who owns 100% of the stock of a regular corporation that manufactures rustic furniture
II.	A single taxpayer with taxable income of $250,000, who is a 50% partner in an accounting firm
III.	A single taxpayer with taxable income of $100,000, who operates an accounting business as a sole proprietorship
IV.	A single taxpayer with taxable income of $125,000, who owns 100% of the stock of an S corporation that produces oak tables