架空线缆可以架设在()。
A.木杆
B.树木
C.钢筋混凝土杆
D.脚手架
E.高大机械
参考答案:A, C
Once harm is _______ to the eco-system, all species will ________, including man himself.
A.made; be in danger
B.done; be dangerous
C.caused; be endangered
D.done; be in danger