7.Sometimes technological progress gives the main system lower costs, while obsolete equipment is kept as standby equipment, rather than being junked, and the costs of producing additional electricity with this obsolete equipment is of course higher.
有时技术进步使主系统成本降低,而废
设备则保留为备用设备,而不是报废,用这些废
设备生产额外电力的成本当然更高。机翻
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