Which of the following industries is the largest producer of primary air pollutants in the US?

Chemical plants

Water treatment plants

Power plants

Smelting plants

Why did large numbers of african migrate to the americas

Some gamma ray bursts are hypothesized to come from mergers of neutron stars or black holes. if this hypothesis is correct, what else should we in principle be able to detect from such mergers? a. gravitiational waves b. x-ray bursts c. significant disruption of gas thousands of light-years away in the surrounding galaxy d. an "afterglow" of bright visible light, lasting for weeks

After world war i, how did the us economy compare to that of germany?