Which of the following are examples of physical systems? a. the gulf stream b. the lincoln tunnel c. the amazon rain forest d. the san andreas fault e. the california gold mine

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