Navigation is the art of measuring distances in order to be able to a. understand time zones b. divide the earth into hemispheres c. travel from one place to another d. separate one day from another

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