53.

---Where's your mother, Helen?

---She _______the flowers in the garden.（）

• A、waters

• B、is watering

• C、watered

• D、has watered

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.