سؤال قراءة ستيب محلول — المفردات في السياق (تدريب 5631)

(1) In an industrial society like the United States, the most important nonfuel resources are iron ore, aluminum ore, copper ore, and minerals containing nitrogen, phosphorus, and potassium used in fertilizers, a lot of energy is used in mining operations and the transportation of ore. To make the task of any physical extraction and transportation worthwhile, the ores must contain enough of the required compound or clement. Some low-grade ore is not usable because of the cost of the mining process. (2) Materials extracted from the earth are processed by screening, separating, washing and grinding. Often, the useful element in an ore is in a chemical form that is not usable and must be changed to a desirable form. For instance, the aluminum in aluminum ore is in the form of aluminum ion. To be useful, the aluminum ion needs to be changed to aluminum metal.