Choice "B" is correct. Sourcing requirements generally refer to content or value added limits on the percentage of labor or materials used in imported products. Compliance with limits may result in tariff reductions.Choice "a" is incorrect. A foreign trade zone contemplates a physical location in which tariffs are waived on imported products until they leave the zone. Foreign trade zones anticipate delay rather than reductions in tariffs.
Choice "d" is incorrect. A value added tax is an incremental tax, not a reduction in tariffs.
Choice "c" is incorrect. An international rebate is not a tariff reduction practice.