New Zealand's main exports come from the nation's farms--wool, meat, butter, cheese, and skins. Many people process farm products in dairies (牛奶房), meat-refrigerating plants, breweries (啤酒厂) and flour mills. Sawmilling is an important industry where logging is cartied on in the forests to make pulp for newsprint and other mills make various kinds of paper.
Most of New Zealand's heavy machinery must be imported, but assembly (装配) plants make automobiles and trucks from imported parts. Woolen goods, carpets, clothing, shoes, furniture and electrical appliances are also manufactured. Imported petroleum (石油) is refined (精炼) at an oil refinery at Whangarei. An aluminum smelter at Blutt, near Invercargill, use hydro-electricity to refine one that is imported from Australia.
New Zealand's coal is used to generate steam, make gases, provide fuel for homes and factories and produce electricity. Sand and gravel (砂砾) used for road building and concrete (混凝土) construction, ranks second to coal. Limestone is used to make fertilizer and cement.
In the first paragraph, "sawmilling" refers to ______.

A. news-print industry
B. shoe-making industry
C. wood-processing industry
D. mineral refining industry