Oil can be poison for

Fluoride is also added to water, which helps in preventing

A. infection

B. sickness

C. fever

D. tooth decay

The tanks that supply water to towns are built at

A. roofs of buildings

B. high towers

C. town level

D. high lands

Polar ice caps are found near the

A. East and West poles

B. East and North poles

C. North and South poles

D. West and South poles

The largest ocean on earth is

A. Pacific Ocean

B. Atlantic Ocean

C. Antarctic Ocean

D. Arctic Ocean

Desalination plant is very expensive because it

A. uses a large amount of fuel

B. is built on mountains and high lands

C. uses electric machinery for desalination

D. is built with expensive material