Sirius has an apparent magnitude of -1.5. canopus has an apparent magnitude of -0.7. which of the following statements is true?

sirius is brighter than canopus.
sirius is hotter than canopus.
the brightness ratio is 1.5 : 0.7.
the absolute magnitude of sirius is 15.

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.