Explanation:

- Cash paid against trade payables involves settling debts related to business operations.

- Operating activities include primary revenue-generating activities.

- Cash payments for trade payables fall under operating activities because it's part of business operations.

- Financing activities involve changes in equity and borrowings, like issuing shares or obtaining loans.

- Investing activities relate to the acquisition or disposal of long-term assets, like buying equipment or property.

- No effect suggests transactions that don't impact the cash flow statement.

Your initial understanding is correct: Option 2—Operating activities.