Which element is part of cash flow activities related to investing?

The correct choice highlights a fundamental aspect of cash flow activities related to investing: buying fixed assets. This action reflects the investment in long-term assets that a company will use to generate revenue over an extended period. Investing cash flows involve transactions that change the long-term asset base of a business, which is crucial for capital formation and operational capacity.

When a company buys fixed assets, such as machinery, equipment, or real estate, it signifies an investment aimed at enhancing productivity or expanding operations. This is characterized by cash outflows associated with asset acquisition, aligning clearly with investing activities.

In contrast, the other options represent different categories of cash flow activities. Paying employee salaries pertains to operating activities as it relates to the daily operational expenditures necessary for running the business. Issuing bonds can be classified under financing activities, as it pertains to raising capital through debt. Collecting rent generally falls under operating activities too, since it typically involves cash generated from regular business operations rather than investment in assets. Hence, buying fixed assets distinctly fits within the framework of investing cash flow activities.