Final answer:
The correct answer is 400,000 units.
Step-by-step explanation:
The subject of this question is Business.
To answer the question, we need to look at the given options and determine which one represents the number of units sold by O'Reilly Manufacturing. The correct answer is option 3) 400,000 units because that is the only option that matches the company's sales figure.
Therefore, O'Reilly Manufacturing sold 400,000 units.