The answer is Investing activities section.
The operating activities section of the statement of cash flows includes transactions related to the primary operations of the business, such as cash receipts from sales of goods and services and cash payments to suppliers and employees. The purchase of land and a building is not related to the day-to-day operations of the business, so it would not appear in this section.
While the purchase of land and a building with a mortgage involves a non-cash financing component (the mortgage), it still represents a cash flow transaction because it involves the acquisition of a long-term asset. Therefore, it does represent a cash flow and should be reported on the statement of cash flows.
The financing activities section includes transactions related to the company's financing, such as issuing debt or equity and repaying loans. While the mortgage itself is a financing activity, the purchase of land and a building is primarily an investing activity. The cash inflow from the mortgage would be reported in the financing section, but the purchase itself is an investing activity.
The investing activities section of the statement of cash flows includes transactions related to the acquisition and disposal of long-term assets, such as property, plant, and equipment. The purchase of land and a building is a capital investment and would be reported in this section.