Which of the following is not a source of cash?

The correct answer is option 2- Purchase of Machinery.

The purchase of machinery is not a source of cash; it represents an outflow of cash as the company spends money to acquire the machinery.

"Issue of shares" and "Sale of Asset" are considered sources of cash. When a company issues shares, it receives cash from investors, and when it sells an asset, it generates cash from the sale.