The basin contains the world's largest expanse of tropical rain forest.
a. salimões
b. rio negro
c. amazon
d. orinoco

Plants in the tundra biomes have had to adapt to live long periods of time without a. cool temperatures b. sunlight c. oxygen d. water

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

The separation of northern ireland from the republic of ireland is an example of