..jka

Wood is considered as ..............

• biofuel

• fossil fuel

• .....

................. is a renewable source of energy

• coal

• water

• natural gas

when a river meats a sea , a ......... is formed

• delta

• canyon

• volcano

canyon may take .......... of years to be formed

• hundreds

• millions

• week

plants need sunlight to grow ?

• false

• true

• ..

sand dunes are formed by erosion only ?

• true

• false

• ....