Detailed Explanation:

Answer: Option 4 — a system of tribunals and a ban on strikes.

The Trade Disputes Act of 1929 was enacted by the British colonial government to regulate industrial disputes in India. It established a formal mechanism through Courts of Inquiry and Boards of Conciliation (tribunals) to investigate and mediate conflicts between employers and workers. Crucially, the Act imposed severe restrictions on strikes: it banned strikes in public utility services (railways, postal services, water supply, etc.) without 14 days' prior notice, and declared general strikes and political strikes illegal. This legislation was primarily aimed at controlling the growing trade union movement and preventing large-scale labor unrest that could challenge British authority.