Percentage of neon in the air is

Solvents used for cleaning electronic circuit boards are

A. chlorofluorocarbons

B. carbons

C. fluorides

D. grease

At every 1 km increase in altitude, the air gets about

A. 10 °C cooler

B. 6.5 °C hotter

C. 6.5 °C cooler

D. 20 °C cooler

The pH of acid rain is

A. more than 5.6

B. less than 5.6

C. 10

D. 7

The atmosphere is divided in to

A. 2 layers

B. 3 layers

C. 1 layer

D. 4 layers

Percentage of oxygen in the air is

A. 0.78

B. 0.21

C. 0.0093

D. 0.0004