填空题 Most countries can produce any product if they are willing (invest) capital. Artificial climates are created in greenhouses (grow) tropical plants. The UK became a sugar producer because war prevented supplies (get) through. Norway has been an oil producer since oil prices forced them (invest) capital in (produce) oil from the North Sea. Japan with few natural resources has become a major industrial nation by (specialize) in (develop) its technology. Only Russia and America could be self-sufficient, (produce) their needs without (import) if they had to. Most other countries have (export) (pay) for their imports. In (do) this, they are concerned with two main problems—their balance of trade and balance of payments.