The soil is depleted first by having crops grown in it and second by natural weathering and bacterial action.土壤首先是被种植其中的作物消耗掉，其次受自然风化和细菌活动的侵蚀。Organic rubbers develop a resinous surface crust through weathering.有机橡胶经过风蚀后,...
...restaurants where coffee pots steamed on their burners.咖啡壶在炉子上冒着热气的餐馆The gas stove has only two burners.这瓦斯炉只有两个瓦斯头.Cautery burners need to be sterilized.烧灼燃烧器必须消毒.Some stoves are oil burners; others are gas burners.有...