The type of tectonic plate boundary that occurs when two plates are colliding into each other is known as a

divergent boundary
convergent boundary
transform boundary
subduction zone

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