Help me pls asap will mark as brainliest if cofrect

Which of there factors contributed most to us westward expansion in the second half of the nineteenth century?

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

Which of the following terms best characterizes the government of somilia