Perform scheduled maintenance service on oil and solid fuel heating systems.
对油和固体燃料加热系统进行定期维护服务。
Which is the most economical fuel for home heating-gas, electricity, or oil?
哪一种燃料用作家庭暖气最经济煤气、电力还是汽油？
Which is the most economical fuel for home heating-gas, electricity, or oil?
哪一种燃料用作家庭暖气最经济煤气、电力还是汽油？
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