Which of the following is not an operating activity?

Proceeds from sale of old machinery.

The correct answer is Option (4) → Proceeds from sale of old machinery. 

• Operating activities are the principal revenue-generating activities of a business — they include all cash flows related to day-to-day operations.
  Examples:

  • Cash receipts from customers

  • Payments to suppliers or employees

  • Operating expenses (selling, distribution, etc.)

• Proceeds from sale of old machinery are not part of normal operations; they are related to the disposal of a fixed asset, which is a non-operating / investing activity.