Water masses on the Earth's surface form about..............

• 30 %

• 50 %

• 71 %

• 97 %

Fresh water represents about of the total volume of water..................

• 0.3 %

• 3 %

• 70 %

• 90 %

..................is among sources of salty water.

• Snow at the two poles

• Ocean

• River

• Ground water

More than............. of known living organisms live in the aquatic environments.

• 25%

• 50%

• 10%

• 75%

The Earth is characterized by the presence of suitable .............................of about 76 cm.Hg.

• gravity

• temperature

• air pressure

• hydrosphere

Water covers about 50 % of the Earth's surface.

• True

• False

The blue colour on the Earth represents the land area.

• True

• False

Salty water represents about 3 % of the total volume of water.

• True

• False

The water of oceans is fresh water.

• True

• False

Water keeps the body temperature constant.

• True

• False