What are the problems of oillamps according to Paragraph 1?
根据第一段，油灯存在哪些问题？
2
The villagers were forced to use oillamps, which are not only expensive but also dangerous because of the harmful gases they produce.
村民们被迫使用油灯，油灯不仅昂贵，而且它们所产生的有害气体十分危险。
3
Coal gas rivaled smoky oillamps and flickering candles, and early in the new century, well-to-do Londoners grew accustomed to gaslit houses and even streets.