Which of the following is not the source of Cash?

The correct answer is option 1- Purchase of Fixed Assets.

The purchase of fixed assets involves an outflow of cash, as it requires the company to spend money to acquire these assets. The other options mentioned - "Issue of Debentures" and "Sale of Fixed Assets" - are both sources of cash. When a company issues debentures, it receives cash from investors, and when it sells fixed assets, it generates cash inflow from the sale.