What figures are 180-degree rotation symmetry

The large connected urbane area from boston to washington, d.c. is often referred to as

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

What factors of japan’s geography make it necessary for it to import so many goods?