题目

China Train GuideQuick Guide on China Train TravelIf you’re looking for an affordable and comfortable way to get around China, train travel is the way to go. Getting train information and cheap train tickets has never been easier. Online train ticket booking makes it easy for travelers to look through China’s train timetable, compare train fares, and look for ticket availability. Once you’ve found a suitable train, you can book online and pick your tickets up at the train station or get them delivered to your home or hotel. Train tickets can be booked online a minimum of 35 minutes and a制约北方地区农业发展的重要的自然因素是（　　） A、地形因素B、位置因素C、水资源不足D、劳动力短缺