Prep.2

.............................is an example of mold fossil

• Foraminifcra

• Ammonites

• Mammoth

All of the following elements have low density except...............

• lithium

• cesium

• potassium

...........................gas harms ozone layer

• $Co_2$

• $O_2$

• $CFC_s$

All of the following are endangered species except............

• ibis bird

• quagga

• bald eagle

The scientist.....................had discovered the main energy levels

• Rutherford

• Mosely

• Bohr

Ionosphere is found in the upper part of...............layer.

• thermosphere

• stratosphere

• mesosphere

Fossils are found preserved in................rocks

• sedimentary

• metamorphic

• igneous

Sodium reacts with water and...................gas evolves

• nitrogen

• oxygen

• carbon dioxide

• hydrogen

Increasing the concentration of ............in drinking water causes blindness.

• mercury

• lead

• chlorine

The most active metal in group ( 1 A) is..................

• sodium

• cesium

• potassium

• lithium