题目选项分析

Edgarton has long been narrowly self-sufficient in both coal and steel. However, as more and more people have moved to Edgarton, more coal needs to be burned to heat their homes. Because coal is an important component of steel, if the influx of new residents continues, Edgarton will soon have to import either coal or steel.

Which of the following is an assumption on which the argument depends?

【选项】Importing either coal or steel will not result in a significantly higher percentage of Edgarton’s incomes being spent on heating than is currently the case.