Keeling's Reports from Mauna Loa Demonstrated ____________

Keeling's reports from Mauna Loa demonstrated ____________

A) that as distances from cities decreased, CO₂ concentrations increased
B) that CO₂ levels have been stable over the last 40 years
C) an increase in tropospheric CO₂ from the 1950s to present
D) the presence of El Niño
E) that sediments deposited on the seafloor can yield clues about past climates