By the early twentieth century, carbon emissions from fossil-fuel burning reached 1 billion tons a year. automobiles, airplanes, and domestic and agricultural energy demands all contributed to the rising trend. in the 1950s, scientists used a new generation of equipment to confirm that carbon-dioxide concentrations were doubling and that this would have the effect of increased temperatures.
what chronology is described in this excerpt?
a. the increase in automobile usage from the early twentieth century through the 1950s
b. the changes in carbon dioxide emissions from the early twentieth century through the 1950s
c. the development of new technologies from the early twentieth century through the 1950s
d. the changes in popular modes of transportation from the early twentieth century through the 1950s