Answer to Question 1
d
Answer to Question 2
A type II supernova occurs when a massive star fuses heavier and heavier elements in its core. Iron nuclei are produced through silicon fusion. Iron does not produce energy when it fuses. When iron fusion begins, no energy is produced to support the rest of the star and the core collapses quickly. A shock wave propagates through the star, and a massive burst of neutrino energy ejects the outer layers of the star in a supernova explosion. A type Ib supernova occurs for very similar reasons to a type II supernova. A type Ib supernova occurs in a star that is part of a close binary system, and has lost significant amounts of mass to a companion. The star is virtually devoid of hydrogen, but goes through the same general pattern of evolution. When the core collapses as a result of iron fusion, the result is the same, except the outer layers of the star that are carried away do not contain significant signatures of hydrogen emission. A type Ia supernova occurs when the mass of a white dwarf exceeds the Chandrasekhar limit. The white dwarf reaches the temperature and pressure required for carbon to ignite. The entire object is consumed as its carbon fuses in a process called carbon deflagration.