Q:

The following is true about ozone?

( A ) It is essential for respiration of animals and plants.

( B ) It absorbs ultraviolet rays.

( C ) Its percentage in air is almost 3 %.

( D ) It is used to disinfect water.

• 1
  A , B and C
• 2
  B and D
• 3
  Only B
• 4
  A and D