阿斯旺水坝建设后引发的生态环境问题是： [ ]
A．下游的农田失去了天然肥料
B．大面积土壤盐碱化
C．淹没农田
D．使水位变化减小
答案：B
Those boys _____ English at the English corner now. [ ]
A. practise speaking
B. practicing spoken
C. are practising speaking
D. are practicing to speak
巷道内人力推车有哪些要求？
