单选题 Overcrowding in cities, towns and villages is another problem caused by over-development of tourism, an outcome of which is ______.

【正确答案】 D

【答案解析】[解析] 此题考查的是对文章第二自然段主题句“Overcrowding in cities，towns and villages is another problem．Traffic jams are an outcome．”的理解，很明显答案是D。