Which phenomenon do bats or dolphins use to find prey, predators or obstacles?

• Refraction of sound

• Formation of beats

• Scattering of sound

• Echo location

Cement is formed by strongly heating a mixture of

• limestone and graphite

• limestone and clay

• chalk and graphite

• clay and graphite

143.

Glass is a

• superheated solid

• supercooled liquid

• supercooled gas

• superheated liquid

The temperature of oxy-acetylene flame is around

• 2800°C

• 3200°C

• 4000°C

• 1500°C

One of the constituents of tear gas is

• ethane

• ethanol

• ether

• chloropicrin

Noise is measure in

• watt

• REM

• centigrade

• decibel

Which of the following resources is renewable one?

• Uranium

• Coal

• Timber

• Natural Gas

Brass contains

• copper and zinc

• copper and tin

• copper and silver

• copper and nickel

Which is the purest commercial form of iron?

• Pig iron

• steel

• Stainless steel

• Wrought iron

In galvanisation iron is coated with

• copper

• zinc

• tin

• nickel