1、多选题：
The challenges of urban water resources include ( ).
选项：
A:High risk of urban water pollution.
B:The standards of urban water quality are high due to the increasing concerns about the safety of urban water sources.
C:Capital and operational costs of water supply for long distance transportation are high.
D:Urban water distribution renders large energy consumption.
答案: 【High risk of urban water pollution.;
The standards of urban water quality are high due to the increasing concerns about the safety of urban water sources. ;
Capital and operational costs of water supply for long distance transportation are high.;
Urban water distribution renders large energy consumption.】

2、判断题：
It is relatively hard to separate salt from water, because ions such as Ca2+，Mg2+，K+are tightly surrounded by water molecules.
选项：
A:错
B:对
答案: 【对】

3、判断题：
Lakes and reservoir waters usually have low water mobility, high turbidity, and relatively stable water quality. ( )
选项：
A:错
B:对
答案: 【错】

4、判断题：
Heavy metals can be concentrated in plant roots or aquatic animals, causing great danger to living organisms. ( )
选项：
A:对
B:错
答案: 【对】

5、判断题：
In the US, different sewage plants follow the same discharge standards. ( )
选项：
A:对
B:错
答案: 【错】