采样断面的布设应充分考虑一下哪些因素？
A、河段的取水口
B、水文及河道地形
C、水量大小
D、水土流失情况
参考答案：A,B,D
若x，y互为相反数，p，q互为倒数，则代数式（x+y）-2pq的值是______．
My mother promised to buy me a great gift,________beyond anything I'd ever imagined. [ ]
A. that
B. it
C. one
D. the one
