Today is Saturday. In the morning, Xiaoyong is sleeping, but the phone rings. He wakes up from his dream. He gets up and goes to the park near his home. He is doing exercise, but it starts to rain. He has to go home. He is doing his homework at home, but the bell rings.

    In the afternoon, Xiaoyong is riding his bike, but suddenly(突然)a little dog runs to him. He falls off his bike. He is so sad.

下列属于人在寒冷环境中的身体变化是（　　）

①皮肤血管收缩   ②增加皮肤的血流量   ③汗腺分泌增多   ④汗液几乎不分泌    ⑤代谢活动增强．

明清时期，平遥古城有“填不平、拉不完的平遥城”之说，又有“进了平遥城，银子元宝绊倒人”之说。这说明当时的平遥城（    ）