Why is the crude birth rate ''crude"?

In the diagram below dab and dac are adjacent angles

You are a scientist who has been sent on a special mission to study plants and animals in south asia! your destination is an important forest in eastern india. you need to travel to 17°n latitude and 83°e longitude.

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