题目

Allan was worried. This was his first time to go traveling ___31___. He didn’t know how to find his seat,___32___ he went to the air hostess(空姐) and asked, ―Could you help me? I can’t find my seat. The air hostess showed ___33___the seat and told him___34___and fasten the seat belt(系好安全带). She told Allan not to move about when the plane was going up. And she also said that Allan’s ears might feel___35___strange, but he didn’t need to ___36___ it because many people felt___37___that. When the plane was flying very high, Allan could stand up and walk around. He co下列不属于生态系统的是（　　）A.一片森林B.一块农田C.一群蚂蚁D.一个池塘