Why are spectral lines useful in classifying stars?

Which characteristics are true of the arabian desert? multiple answers choose all answers that are correct. a. is mostly below sea level b. covers almost the entire arabian peninsula c. contains the largest sand sea in the world d. has very few people living there

Explain the value of statistics and other data to positive economics and to normative economics

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