单选题 Deserts and high mountains have always been a______to the movement of people.
【正确答案】 B
【答案解析】解析:barrier(to)n.屏障;障碍,障碍物。restraint n.(感情、情绪、行为的)抑制,限制,克制。handicap n.(身体或智力方面的)缺陷:障碍,不利条件。disadvantage(over)n.不利地位,不利条件。