本题考查从属连词的用法。分析两个句子内容可知，二者是让步的关系，即：即使他厌倦了……，但他还是……。所以可以用although或者even though来连接两个句子。所以答案可以是Carlos decided to renew the lease on his New York apartment even though he was growing tired of city life.或者Carlos decided to renew the lease on his New York apartment although he was growing tired of city life. 

句意：卡洛斯决定续租他在纽约的公寓，尽管他已经厌倦了城市生活。