The pH of acid rain is

Solvents used for cleaning electronic circuit boards are

A. chlorofluorocarbons

B. carbons

C. fluorides

D. grease

Percentage of neon in the air is

A. 0.0018

B. 0.0019

C. 0.002

D. 0.0021

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 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