what concentration in the air has increased dramatically over the last decade?
zinc CO2 h2o CFCs lungs coal O2 CO 2
A B C D E F G H
Carbon dioxide, CO2, is usually a harmless gas.
CO2 concentrations in the air have increased over the last decade dramatically
what concentration in the air has increased dramatically over the last decade? (A) zinc (B) CO2 (C) h2o (D) CFCs (E) lungs (F) coal (G) O2 (H) CO 2