Percentage of oxygen in the air 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 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