Final answer:
A decrease in owner's equity may result from a withdrawal of cash by the owner or a purchase of office supplies for cash.
Step-by-step explanation:
A decrease in owner's equity may result from a variety of activities. To address the given options specifically:
- An investment of cash in the business by the owner increases owner's equity, not decreases it.
- A withdrawal of cash in the business by the owner, also known as a draw, decreases owner's equity.
- Purchasing office supplies for cash represents an expense, and by reducing the company's assets without any associated revenue, it decreases owner's equity.
- Revenue derived from sales of goods or services increases owner's equity.
Therefore, the activities resulting in a decrease in owner's equity from the given choices are a withdrawal of cash by the owner and the purchase of office supplies for cash.