根据短文内容选择答案。

      My name is Jack. I am a pupil of Grade One. I'm in No.1 Middle School. On weekdays I get up at six o'clock. I have breakfast at seven and then I go to school by bike. We begin our class at eight o’clock in the morning. We have four classes in the morning and three in the afternoon.

      At noon, I have lunch at home. Classes are over at four fifteen in the afternoon. After class, we often play football in the afternoon. I go home at about five. I have supper at about six thirty in the evening. I do my homework at seven thirty. At weekends, I watch TV. I often go to bed at ten. I'm very happy.

（2015•海南）近年来，我国服务贸易的进出口总值占商品进出口总值的十分之一左右，且在加入世界贸易组织的十余年中一直处于逆差状态。这种状况长期存在的主要原因是（    ）