Which of the following is a common tool used in protectionist policies?

Protectionist policies are implemented by governments to restrict foreign competition and support domestic industries. A common tool in these policies includes subsidies, which are government grants or financial aid given to local businesses to make their products more competitive against international imports. Tariffs are another essential tool; they are taxes imposed on imported goods, making them more expensive and thereby incentivizing consumers to purchase domestic products instead. Quotas limit the quantity of a specific good that can be imported, ensuring that local producers have a guaranteed market share by controlling import levels.

Each of these methods serves the overarching goal of protectionism: to shield local industries from foreign competition and promote economic growth within the country. By combining these tools—subsidies, tariffs, and quotas—governments can create a more favorable environment for their domestic industries against external competition. Therefore, recognizing that all these measures function as common protective tools justifies the selection of "All of the above" as the correct answer.