What happens when ice dams break?（）

• A、They may quickly block the river.

• B、The ice covering the river may melt fast.

• C、A larger ice dam may soon be formed.

• D、The areas down the river maybe flooded

What have scientists achieved in dealing with floods?（）

• A、They have prevented many rivers from flooding.

• B、They have reduced the damage caused by floods

• C、They have learned much about conditions for flooding.

• D、They have found most of the ice damson the river.

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