Which of these is the likely progenitor of a type II supernova?
A) a mass-transfer binary, with the white dwarf already at 1.3 solar masses
B) a contact binary, with the neutron star at 2.3 solar masses
C) an evolved red giant which is just starting to make silicon in its core
D) two white dwarfs in a contact binary system
E) an evolved blue supergiant that is about to experience the helium flash
Question 2
How did Alfred Wegener first notice the possibility of plate tectonics? What lies in the gap he noted?
What will be an ideal response?