a) Income from property and income from personal services are both considered ordinary income.

The two prerequisites of ordinary income typically include:

b) Cash or convertible to cash and be a real gain.

Ordinary income generally refers to income that is taxable at marginal rates and includes items like salaries, tips, bonuses, commissions, rents, and other similar types of earnings that can be readily converted to cash or represent a genuine gain. Therefore, the correct answer is:

b) Cash or convertible to cash and be a real gain.

However, it's important to note that the term "ordinary income" in a tax context usually encompasses income streams that are taxable at the recipient's marginal tax rate, such as wages, salaries, and other similar forms of earnings.