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C is corrent. The requirement is to identify the nature of the producer price index. The price index measures the combined price of a selected group of goods and services for a specified period in comparison with the combined price of the same or similar goods for a base period. The US government’s producer price index (PPI) is an example. It measures the price of a basket of 3,200 commodities at the point of their first sale by producers.
A is incorrect because the export price index measures price changes for all products sold by domestic producers to foreigners.
B is incorrect because the consumer price index measures the price of a fixed market basket of goods purchased by a typical urban consumer.
D is incorrect because the producer’s price index measures the price of a basket of commodities at the point of the first commercial sale, not the price of all goods purchased by producers.